The nutritional, cognitive, emotional, and immunologic benefits of human breast milk
and breastfeeding are significant and well documented [1]. Human milk protects against
specific pathogens (viruses, bacteria, and parasites) as well as separate clinical
illnesses (eg, necrotizing enterocolitis, bacteremia, meningitis, respiratory tract
illness, diarrheal disease, and otitis media) [2]. The benefits of breast milk make
it one of the most important factors in protecting infants against the morbidity and
mortality of infectious diseases [2], [3], [4], [5], [6], [7], [8]. Numerous factors
within human breast milk act in a complementary fashion to protect against infection.
They contribute to the infant's immune protection through various mechanisms, including
improved growth of nonpathogenic flora, decreased colonization with enteropathogens,
enhanced development of the respiratory and intestinal mucosal barriers, specific
factors against individual organisms (eg, secretory IgA [sIgA]), functioning immune
cells (eg, neutrophils, macrophages, T and B lymphocytes), decreased inflammatory
reaction, and immunomodulation [2], [9], [10], [11].
Microorganisms also have been identified in colostrum and breast milk. Few are readily
transmitted through breast milk to cause clinically significant infections in infants
and children (eg, HIV1, human T-lymphotrophic virus I [HTLV-I]). Others have been
reported to cause infection in the infant rarely, after transmission through breast
milk (eg, group B streptococci). Any decision about possible infection of an infant
or child through breast milk should weigh the tremendous benefits of breastfeeding
against the potential risk for transmission and the possible severity of the illness.
This article presents an overview of the considerations for breast milk and infection,
focusing on the most important organisms that are transmitted through breast milk
(HIV1, HTLV-I, and cytomegalovirus [CMV]) and touching on other organisms that are
important in neonates and infants or that have captured public notice. The basic assumption
is that breastfeeding is contraindicated rarely during maternal infection. The few
exceptions are specific organisms with clear evidence of transmission through breast
milk that cause significant morbidity and mortality because of infection through breast
milk.
Essential concepts
Several factors must be considered to prove that breast milk is the mechanism of transmission
for a clinically significant infection in the infant (Box 1)
.
Box 1
Factors to prove infection transmission through breast milk
1.
Identify the infectious agent in the colostrum or breast milk using culture, nucleic-acid
detection, antigen detection, or other methods.
2.
Postulate a reasonable mechanism of infection given the current knowledge about the
organism and the host's response to it, including timing and pathophysiology.
3.
Characterize the clinical manifestations of the illness in the mother and the infant.
4.
Demonstrate the occurrence of infection in the mother and the infant by culture, nucleic-acid
identification, or immunologic response.
5.
Confirm that the organisms identified in the mother and infant are identical based
on serotype, sensitivity pattern, nucleic-acid sequence, and other factors.
6.
Document that the risk for infection is greater in breast-fed infants than in formula-fed
infants.
7.
Characterize a dose–response relationship between the quantity of organisms in the
breast milk as well as the amount of breast milk ingested and the frequency of transmission
or the severity of the infection in the infant.
8.
Exclude other possible mechanisms of transmission.
9.
Prove the transmission through breast milk by reproducing the process in animal or
human studies.
Excluding other probable mechanisms of transmission can be challenging, especially
in the neonatal period. The organisms that are a concern for transmission through
breastfeeding are transmitted more commonly prenatally, perinatally, and postnatally
through other mechanisms. Congenital infection can occur in any trimester, depending
on the organism. The timing of infection also significantly affects the clinical course
of the infection in the fetus or newborn (eg, asymptomatic, fetal demise, prematurity,
clinical disease present at birth, or late presentation). Perinatal infections commonly
occur from exposure to blood or body fluids and contact with pathogens from the maternal
genitourinary and gastrointestinal tracts. The likelihood that the exposed infant
will be infected varies significantly with the specific organism and various host
factors (eg, passively acquired antibody levels in the infant). Postnatally acquired
infections are transmitted most commonly through contact with caregivers (eg, parents,
relatives, visitors, health care providers), the environment (eg, medical equipment,
other fomites), or breast milk, depending on the organism [12].
The timing of the infection in the mother and the infant is often crucial to documenting
the mechanism of transmission. In most infectious situations, the exposure of the
infant and mother to child transmission has occurred before the illness is diagnosed
in the mother (eg, measles, Coxsackievirus infection) and frequently occurs before
the mother becomes ill (eg, chickenpox, hepatitis). Proscribing breastfeeding at that
point may not prevent infection in the infant and will diminish significantly the
effect of breast milk to limit or modify the illness in the infant. The timing of
the infection in the mother can influence significantly the risks to the infant (eg,
primary HIV or CMV infection before pregnancy, during pregnancy, or postnatally, ie,
during lactation).
The approach to any suspected infection in the breastfeeding mother–infant dyad should
be systematic (Box 2)
. The mother's initial immunologic response to the infection may add specific factors
to the breast milk that can prevent infection or ameliorate the illness. Many maternal
illnesses associated with fever do not require separation of the mother and infant
(eg, engorgement of the breasts, atelectasis, nonsuppurative phlebitis, or urinary
tract infection) or additional precautions to protect the infant.
Box 2
Approach to a suspected infection in a breastfeeding mother
1.
Suspect particular infectious agents based on the clinical presentation.
2.
Initiate a directed diagnostic work-up to identify the etiologic cause of the infection.
3.
Consider the probable mechanisms of transmission, the known virulence of the likely
infectious agents, and the susceptibility of the infant.
4.
Institute preliminary infection-control precautions (including temporarily holding
or continuing breastfeeding) based on the clinical syndrome, site of infection, probable
mode of transmission, and infant's susceptibility.
5.
Start empiric therapy in the mother as indicated by the severity of the mother's illness.
6.
Consider preventive or empiric therapy for the infant when the risks for infection
and significant disease are high.
7.
Modify the empiric therapies and precautions based on the agent identified as the
cause of the infection in the mother.
8.
Observe the mother for response to therapy and the infant for signs and symptoms of
infection requiring treatment.
Another important consideration relative to breast milk and infection is medications
in breast milk. A thorough review of antimicrobial agents and breast milk is outside
the scope of this article. Most antimicrobial agents used to treat infection can be
used in infants and children. Additional amounts that are ingested by the infant in
breast milk are usually insignificant compared with doses used to treat the infant.
In almost all cases, an antimicrobial agent that is appropriate for treating the mother
and compatible with breastfeeding can be selected.
Infection-control issues
Infection-control guidelines are intended for hospitals, but the principles of epidemiology
can be applied to any infectious situation, even in the home, and can facilitate logical
and reasonable use of interventions to prevent transmission of infection to an infant.
Newer concepts and terminology have been proposed recently [13]. Standard precautions
include avoiding direct contact with blood and body fluids, nonintact skin, and mucous
membranes of every patient, regardless of the patient's diagnosis, based on the idea
that infection can be transmitted without an identified infection and from unidentified
sources. Standard precautions emphasize careful handwashing with every patient contact
and the use of appropriate barriers when contamination with body fluids is more likely
(eg, gloves, masks, glasses). Breast milk is not considered a potentially infectious
body fluid under these guidelines. Careful handwashing before and after breastfeeding
is always appropriate, as are selected barriers (mask, gown or clothes, bandages)
to prevent infant contact with other body fluids of the mother with a specific infection.
Washing the breast before or after breastfeeding is unnecessary and may irritate the
breast.
Specific contact, droplet, or airborne precautions are used for certain illnesses
and microorganisms based on the predominant mode of transmission [14]. Airborne precautions
are used to prevent transmission through droplet nuclei (ie, respiratory particles
less than 5 μm in diameter that can contain microorganisms). Respiratory protective
devices (requiring personal fitting and seal testing) are recommended for illnesses
such as measles, varicella, disseminated zoster, and tuberculosis. Because infants
cannot wear such devices, infants of mothers with these infections should be separated
temporarily from the mother during the infectious period, regardless of the mode of
feeding. The infant can receive the mother's expressed breast milk through a bottle
(given by another individual), except when there are lesions of varicella-zoster or
tuberculosis on the breast, and in the case of measles, where breast milk should be
held until the infant has received immunoglobulin.
Droplet precautions are used for larger respiratory droplets that travel only short
distances in the air and are transmitted more frequently by direct contact with mucous
membranes, hands, or objects contaminated with respiratory secretions. Use of a surgical
mask (by the individual with the infection) to limit the spray of droplets and touching
of mucous membranes as well as careful handwashing are the primary interventions.
Droplet precautions should be used for adenovirus, diphtheria, influenza, Haemophilus
spp, mumps, mycoplasma, Neisseria spp, pertussis, respiratory illnesses, rubella,
and Streptococcus spp. Timing is crucial relative to the institution of such precautions
to prevent disease. In the case of parvovirus, a previously well mother is unlikely
to be infectious after onset of the rash [15]. Expressed breast milk can be given
to the infant in most cases.
Contact precautions are used to prevent transmission by direct or indirect contact
with potentially pathogenic organisms. Indicated interventions can include the use
of gloves and gowns, handwashing before and after using such barriers, and cohorting,
separation, or a private room. Contact precautions can be used for many organisms
(eg, diarrheal agents, multi-drug–resistant organisms). The use of expressed breast
milk is acceptable in most situations where contact precautions are recommended, with
Ebola virus infection or Lassa fever as notable exceptions [16].
Bacterial infections
Bacterial infections in neonates and infants are common. Systemic bacterial infections
occur in the neonate with a frequency of one to five episodes in 1000 live births.
The timing of infection in the neonate is divided commonly into early-onset (before
7 days of age, especially less than 24 hours of age), late-onset (7–30 days of age),
and very late–onset (after 30 days of age). The predominant organisms of early-onset
are group B streptococci and enteric bacilli, especially Escherichia coli. Less common
early-onset pathogens include other streptococci, Enterococcus spp, Listeria spp,
Haemophilus influenzae, Streptococcus pneumoniae, Chlamydia spp, and other organisms
in the maternal genital flora. These organisms can cause late- or very late–onset
bacterial infections. Additional gram-negative bacilli are resistant frequently to
antibiotics, and Staphylococcus aureus and coagulase-negative strains become more
frequent, especially during hospitalization of a neonate or infant. Transmission of
these organisms from mother to child through breast milk is relatively rare compared
to the transmission perinatally during delivery, or through direct contact with the
mother, family, or health care providers after birth. Table 1
lists selected organisms.
Table 1
Breastfeeding issues for selected bacterial maternal infections
Organisma
Predominant modes of transmissionb
Usual timing of infectionc
Evidence for transmission in breast milk
Clinical significanced
Clostridium botulinum
Food-borne
NA
None
BF/BM
Toxin-mediated disease
Chlamydia trachomatis
Contact-genital, secretions
Perinatal
None
BF/BM
Escherichia coli
Contact—GI tract or stool
Perinatal
None
BF/BM
Haemophilus influenzae
Contact
NA
None
Delay BF 24-hr therapy in mother; BM Rifampin prophylaxis for the infant.
Droplets
Listeria monocytogenes
Contact—GI tract
Perinatal
None
BF/BM
Food-borne
Postnatal
Mycobacterium tuberculosis
Airborne
Postpartum (perinatal and congenital are rare)
Only with TB
With active TB, delay BF for 14 days; maternal therapy or PI, BM.
Mastitis and lesions on the breast
Droplet
Infant—isoniazid prophylaxis.
Neisseriae gonorrheae
Contact—genital, oral, rectal
Perinatal (postnatal is rare)
None
Ceftriaxone—no delay, BF / BM.
Body fluids
Other medications—delay 24-hr maternal therapy, BM.
Staphylococcus aureus
Contact
Postnatal
Lesions on the breast or mastitis
Delay 24-hr maternal therapy, BM.
Contaminated, stored breast milk
Avoid BM with breast lesions or MRSA.
Coagulase- negative staphylococci
Contact
Postnatal (premature, sick neonates; IV lines, antibiotics)
None
BF/BM
Group B streptococci
Contact—genital tract, secretions
Prenatal
Case reports, rare
Preventive therapy.
Perinatal
Delay 24-hr maternal therapy, BM.
Postnatal
Empiric prescription for infante
This is a selected, limited list intended to consider some important bacteria that
cause infection in the neonate or infant and possible issues related to breastfeeding
and breast milk.
Abbreviations: BF, breastfeeding is appropriate; BM, expressed breast milk is appropriate;
GI, gastrointestinal; IV, intravenous; NA, Not applicable; PI, period of infectivity;
TB, tuberculosis.
a
Bacteria that cause various clinical illnesses in the infant and the mother; the specific
illnesses are too numerous to list.
b
For breastfeeding and non-breastfeeding situations; does not include all possible
or reported modes of transmission (airborne, body fluids, contact, droplet, food-borne).
c
Does not include all possible times of transmission. If “NA” the timing of infection
is not associated frequently with pregnancy, delivery, or neonates and infants.
d
Notes the appropriateness of breastfeeding or use of breast milk when the mother has
specific bacterial infection.
e
Refer to the text for explanation.
Botulism most frequently occurs between 6 weeks and 6 months of age and primarily
before 12 months of age, with the youngest patient in the literature 6 days of age
[17]. Botulism is caused by the neurotoxin produced by Clostridium botulinum. Arnon
and colleagues [18] reviewed 50 patients hospitalized for botulism in California and
the breast-fed infants were older at diagnosis than formula-fed infants, and had milder
disease. In cases of sudden infant death syndrome associated with botulism, no infants
were breast-fed within 10 weeks of death. An association with the introduction of
solid foods has been suggested. Honey and corn syrup often are implicated because
they may contain C botulinum spores. The apparent immunologic benefit of breast milk
may be caused by more acidic stools (pH 5.1–5.4) and increased Bifidobacterium species
in the stools of breast-fed infants, limiting the presence of C botulinum or spores.
Botulinum toxin production declines with lower pH. No evidence suggests that the organism
or the toxin is transmitted through breast milk.
Chlamydia infection may be the most frequent sexually transmitted disease in the United
States. Perinatal infection in the infant produces conjunctivitis and pneumonitis
and is caused primarily by colonization of the infant when passing through the birth
canal. Specific sIgA has been identified in colostrum and breast milk. There is no
evidence for transmission through breast milk.
Escherichia coli is a common cause of neonatal systemic bacterial infection as well
as urinary tract infections and bacteremia in infants. E coli is ubiquitous in the
mother and infant's environment. Breast milk has never been documented as a source
of E coli infection.
Haemophilus influenzae infections have decreased significantly in countries with widespread
use of the H influenzae conjugated vaccines (HibTITER, PedvaxHIB, Comvax, ActHIB,
OmniHIB) [19]. Transmission is through direct contact and respiratory droplets; there
is no evidence for its transmission through breast milk. Breast milk seems to limit
colonization of H influenzae in the infant's throat [20]. In the unusual situation
of infection in a breastfeeding mother with an incompletely immunized infant, then
chemoprophylaxis is indicated for all household members, including the infant [21].
Temporary separation of the infant and mother is appropriate during the first 24 hours
of the mother's antimicrobial therapy, after which breastfeeding can resume. Expressed
breast milk can be given to the infant in the interim.
Listeriosis during pregnancy infrequently causes premature delivery or stillbirth.
Perinatal infection is an uncommon cause of severe disease in the neonate with transmission
through transplacental spread, infected amniotic fluid, or contact with the organism
in the maternal genital tract. No published information suggests transmission of Listeria
monocytogenes through breast milk. Breastfeeding or use of expressed breast milk from
the mother with Listeria infection is appropriate, including the selection of antimicrobial
agents that are compatible with breastfeeding to treat the mother.
Neisseria gonorrhoeae is transmitted during passage through the birth canal and infrequently
from postnatal contact with the mother or her partner. There is no documented risk
for transmission in breast milk. Breastfeeding can continue when the mother is treated
with ceftriaxone (Rocephin), but a temporary cessation (first 24 hours of maternal
therapy) of breastfeeding and breast milk should occur when other antibiotics are
used.
Staphylococcal infection usually occurs late in the neonatal period. Forty to ninety
percent of infants in the nursery at 5 days of age will be colonized with Staphylococcus
aureus
[22]. Staphylococcus aureus caused nursery outbreaks in the past. Postnatal contact
with mothers, health care workers, and contaminated, unpasteurized, banked breast
milk were the identified sources of infection [23]. Staphylococcus aureus is a common
cause of mastitis in the mother. There is one reported case of staphylococcal scalded
skin syndrome in an infant whose mother had a skin lesion caused by staphylococcus
on her areola [24]. No attempt to identify the toxin or the organism in the breast
milk was made. This case reinforces close, continued observation of the infant (breast-
or formula-fed) when there is a documented maternal infection. In a case of toxic
shock syndrome in a mother at 22 hours postpartum, the breast-fed infant remained
well through 60 days of age. Staphylococcal enterotoxin F (SEF) was identified in
breast milk on days 5, 8, and 11, but Staphylococcus aureus was isolated only from
the mother's vagina and not the breast milk [25]. SEF is inactivated by pepsin at
pH 4.5. It is probably inactivated in the stomach, presenting no risk to the infant.
Methicillin-resistant Staphylococcus aureus (MRSA) is more frequent than in the past.
Skin and nares are the predominant sites of colonization. No treatment regimen to
eradicate colonization has proved highly successful. Current regimens include oral
systemic therapy with one or two sensitive antibiotics, topical antibiotics twice
daily to the nares, and intermittent bathing with hexachlorophene (pHisoHex) or a
similar agent. In the face of maternal Staphylococcus aureus infection, use of expressed
breast milk is appropriate during a temporary 24-hour separation of mother and infant
at the initiation of maternal antimicrobial therapy.
Coagulase-negative staphylococcal infection causes late-onset disease in susceptible
neonates. Factors associated with increased risk for this infection include prematurity,
low birth weight, very low birth weight, invasive therapies (eg, intravenous lines,
chest tubes, surgery, dialysis), antibiotic use, and prolonged hospitalization. Colonization
rates are as high as 60% to 90% for infants hospitalized at 2 weeks of age, in selected
nurseries. There is no difference in the infection or colonization rates for formula-fed
and human milk–fed infants. Breast milk can be given and may provide significant other
benefits to these susceptible infants.
Group B streptococcus (GBS, Streptococcus agalactiae) is transmitted primarily in
utero and during delivery. The revised guidelines proposed by the American Academy
of Pediatrics committees on Infectious Diseases and the Fetus and Newborn use several
variables to identify increased risk for GBS infection in the neonate and recommend
intrapartum prophylaxis for those infants at high risk [26]. Colonization of the infant
during the postnatal period occurs [27], [28]. Although many infants are colonized,
few develop disease [29]. Acquisition of GBS through breastfeeding or breast milk
is rare, but has been documented in cases of late-onset GBS disease [30], [31]. Butter
and DeMoor [32] demonstrated GBS in the nose and throat of infants when GBS also was
cultured from the mother's breast. It is more likely that transmission occurs through
contact rather than the organism passing in the breast milk. A mother or infant colonized
or infected with GBS should be managed with standard precautions during hospitalization.
Routine culturing of the breast or breast milk and therapy to eradicate colonization
have not proved useful. GBS has not been associated with outbreaks in the nursery.
When the mother begins treatment for GBS disease (most often endometritis), temporary,
24-hour separation of the mother and infant should occur with the provision of expressed
breast milk for the infant.
Tuberculosis (TB) is uncommon in the United States, but remains a significant and
common disease worldwide. Congenital TB is extremely rare, with fewer than 300 reported
cases in the literature. TB mastitis is also rare. Starke [33] has summarized the
evaluation and treatment of a pregnant woman with a positive tuberculin skin test.
The primary concern is the postnatal exposure of the infant through droplets or droplet
nuclei by the mother or another household member with active pulmonary TB. Complete
evaluation of the suspected person to determine their TB status (active disease with
or without positive cultures and smears) and testing of all household contacts are
the first steps. Breast-fed and formula-fed infants are equally at risk from respiratory
transmission. Separation of the infant from any case of active pulmonary TB is appropriate.
Once adequate therapy in the mother has begun and the mother is determined to not
be infectious, the infant and mother may have contact. Observation of the mother and
infant should continue through the completion of treatment for the mother. Transmission
of TB in breast milk has never been documented in the absence of TB mastitis. Expressed
breast milk can be given safely to the infant because antituberculous medications
can be used in infants. The only contraindication to using breast milk is in the mother
who has TB mastitis. Prophylactic isoniazid (Nydrazid, Laniazid) therapy for the infant
prevents TB infection in infants. Once both the mother and infant are being treated
and closely observed, they can be in contact [34].
Viral infections
Most significant viral infections in neonates or infants occur through transplacental
or intrapartum transmission. The risk for transmission from mother to child varies
significantly if the maternal infection is a primary infection (eg, herpes simplex
virus [HSV], HIV1), a secondary (reactivation) infection (eg, HSV, CMV) or a chronic
infection (eg, hepatitis B, HIV1, HTLV-I) during pregnancy or lactation. The transmission
of infection through breast milk is well documented for CMV, HIV1, and HTLV-I. Exposure
to small amounts of virus in human milk multiple times a day over the period of breastfeeding
(months to years) probably contributes to the high rate of transmission of CMV, HIV1,
and HTLV-I through breast milk. For most other viruses, transmission through breast
milk is rare (Table 2)
.
Table 2
Breastfeeding issues for selected viral maternal infectionsa
Virusa
Predominant modes of transmissionb
Usual timing of infectionc
Evidence for transmission in breast milk
Clinical significanced
Cytomegaloviruse
Contact—body fluids
Congenital, perinatal, postnatal
Culture; CMV-DNA PCR
Full-term infants: BF/BM.
Premature, LBW, VLBWf
Enteroviruses (coxsackie virus, enterovirus, poliovirus)
Contact—fecal-Oral
Perinatal, postnatal
None
BF/BM
Hepatitis A
Food; water, contact—body fluids
Postnatal
One case report
BF/BM
Immunoglobulin
Hepatitis Be
Blood; body fluids; sexual
Perinatal
Hepatitis B Surface Antigen
Routine prevention with HBV vaccine and hepatitis B immunoglobulin, then BF/BMg
Hepatitis C
Blood; body fluids
Prenatal, perinatal
? Possible HCV-RNA
BF/BM (increased transmission if coinfected with HIV)
HSV1, HSV2
Contact
Perinatal (congenital, postnatal)
Transfer only with breast lesions
BF/BM (except with breast lesions)
HIV1
Blood; body fluids; sexual
Perinatal, prenatal, postnatal
HIV-RNA PCR; culture
Avoid BF/BMe
HIV2
Blood; body fluids; sexual
Prenatal, perinatal
Limited information
Avoid BF/BM (early weaning may be appropriate)
HTLV-I
Blood; body fluids
Postnatal, prenatal, perinatal
HTLV-I–RNA PCR
Avoid or limit BF/BM to less than 6 mo
Parvovirus
Contact; body fluids
Prenatal
Unknown
BF/BM
Respiratory syncytial virus
Droplets; contact
Postnatal (susceptible neonates and infants)
None; possible benefit of BM
BF/BM
Palivizumabh
Varicella-zoster virus
Contact; droplets
Postnatal (rare congenital or perinatal)
Only with lesions on breast; VZV-DNA
Avoid BF for PI
BM if no breast lesions Varicella-zoster immunoglobulin for infant
This is a selected, limited list intended to consider some important viruses that
cause infection in the neonate or infant and possible issues related to breastfeeding
and breast milk.
Abbreviations: BF, breastfeeding; BM, expressed breast milk; HBV, hepatitis B virus;
HCV, hepatitis C virus; LBW, low birth weight; PCR, polymerase chain reaction; PI,
period of infection; VLBW, very low birth weight; VZV, varicella-zoster virus.
a
Viruses that cause a various of clinical illnesses in the infant and the mother; the
specific illnesses are too numerous to list.
b
For breastfeeding and non-breastfeeding situations; does not include all possible
or reported modes of transmission (airborne, body fluids, contact, droplet, food-borne).
c
Does not include all possible times of transmission.
d
Notes the appropriateness of breastfeeding or use of breast milk when the mother has
a specific viral infection.
e
Refer to the text for more explanation.
f
CMV-positive breast milk should be avoided in these infants if they lack CMV-IgG.
They are at greater risk to develop CMV-related disease.
g
Breast-fed infants who have received hepatitis B vaccine with or without hepatitis
B immunoglobulin as indicated by maternal hepatitis B status are at no greater risk
for HBV infection than formula-fed infants (who also should have received hepatitis
B vaccine with or without hepatitis B immunoglobulin as indicated by maternal hepatitis
B status).
h
Palivizamab is indicated for certain children at high risk for respiratory syncythial
virus infection, regardless of feeding mode [16].
CMV is the most common cause of congenital infection in the United States. Approximately
1% of all infants excrete CMV in their urine at or soon after birth (less than 3 weeks
of age). About 5% of the CMV congenitally infected infants will manifest disease at
birth and 15% will manifest congenital infection later (eg, progressive late-onset
hearing loss, learning disability) [35]. Perinatal infection occurs through direct
contact or body fluid contact at delivery, but is associated rarely with clinical
illness in full-term infants. Postnatal infection occurs through breastfeeding or
contact with infected body fluids, most frequently during play with other infants,
especially in day-care settings. Infection through breast milk rarely results in significant
disease in full-term infants. The normal acquisition of transplacental maternal antibodies
against CMV protects full-term infants of CMV-positive mothers. Rarely, primary CMV
infection occurs in the mother around delivery or during lactation, which increases
the risk for illness in the infant because of a lack of anti-CMV antibodies available
to the infant. CMV is identifiable in breast milk at various rates in CMV-positive
mothers, probably because of variation in the testing and sampling techniques and
the intermittent nature of reactivation and excretion of the virus. Postnatal exposure
of susceptible infants (ie, infants without passively acquired maternal antibodies
against CMV: premature infants, infants of CMV-seronegative mothers, and immunodeficient
infants) can lead to severe disease (hepatitis, pneumonitis) [36], [37].
Vochem and colleagues [38] described CMV transmission in breast milk–fed, premature
infants when the mother had virolactia (17/29, 59%) as compared with infants without
CMV identified in the breast milk (0/27). Five of the infants infected before 2 months
of age developed an acute sepsis-like picture with apnea, bradycardia, hepatitis,
leucopenia, and prolonged thrombocytopenia compared with infants infected after 2
months of age, who exhibited only mild disease. Yasuda and colleagues [39] and Sharland
and colleagues [40] demonstrated decreased infection and disease in premature infants
who received CMV-positive breast milk when the milk was stored at −20°C or pasteurized.
No prospective, controlled trials have demonstrated the efficacy of such treatments
of breast milk in preventing CMV infection in premature infants. CMV-seropositive
mothers can breastfeed their full-term infants safely. Exposure of CMV-seronegative
or premature infants to CMV-positive blood products or human milk (from donor or mother)
should be avoided.
Hepatitis in the pregnant or lactating mother requires complete evaluation and identification
of a specific etiologic agent. Many viruses can cause hepatitis, most frequently hepatitis
A, B, and C viruses, CMV, and Epstein-Barr virus, and there are several nonviral causes
(toxic, autoimmune, and others).
Transmission of hepatitis A virus (HAV) in breast milk has been implicated in one
case report [41]. It is uncertain how frequently HAV can be isolated from breast milk.
There is no evidence for chronic HAV infection and the infection in infants is usually
mild. Exposure of the infant usually has occurred before the diagnosis is made in
the mother. There is no reason to stop breastfeeding. The infant of a mother with
recently diagnosed HAV infection should receive immunoglobulin and HAV vaccine (Havrix,
Vaqta).
Chronic hepatitis B virus (HBV) infection develops in 90% of infants infected before
or during birth. Children infected between 1 and 5 years of age develop chronic HBV
infection about 30% of the time. The sequelae of chronic HBV infection include chronic
active infection, chronic persistent hepatitis, cirrhosis, and hepatocellular carcinoma.
Transmission is primarily through blood or body fluids. Transmission of HBV occurs
with breast milk and hepatitis B surface antigen has been demonstrated in breast milk.
There is no difference in seroconversion rates for formula-fed and breast-fed infants
[42], [43]. The appropriate administration of hepatitis B immunoglobulin (HBIg) and
HBV vaccine (Recombivax HB, Engerix-B) at birth for infants born to hepatitis B surface
antigen–positive mothers prevents transmission in more than 95% of cases, regardless
of the mode of feeding [44]. Breastfeeding can continue along with the administration
of HBIg and HBV vaccine.
Hepatitis C virus (HCV) infection leads to chronic infection in 70% to 85% of cases,
regardless of the timing of infection, and leads to the same potential sequelae as
does HBV. Transmission occurs through blood and blood products, intravenous drug use,
probably body fluids contaminated with blood, and sexual transmission when there are
other STDs or a high viral load in blood or body fluids. Congenital and intrapartum
transmission occurs. Factors that seem to increase risk for such transmission include
high maternal viral load, maternal coinfection with HIV, and prolonged rupture of
membranes with vaginal delivery [45], [46], [47], [48], [49], [50], [51], [52], [53].
The frequency and the easy diagnosis of HCV infection in infants still need to be
worked out. Transmission of HCV infection through breast milk has not been proved,
and transmission rates seem similar in formula-fed and breast-fed infants. Published
studies have not controlled for variables such as maternal HCV-RNA serum viral loads,
amount of virolactia, exclusive or partial breastfeeding versus exclusive formula
feeding, and duration of breastfeeding [45], [46], [47], [51], [52], [53], [54]. Additional
controlled trials are needed to delineate the importance of different factors contributing
to or limiting transmission from mother to child. Current Centers for Disease Control
and Prevention guidelines do not consider maternal HCV infection a contraindication
to breastfeeding, although they suggest that cracked or bleeding nipples may increase
risk for transmission [55]. Regardless of the etiologic cause of maternal hepatitis
(A, B, or C), the theoretic risks for transmission through breast milk should be discussed
balanced with the benefits of breast milk, so the mother and parents can make an informed
decision concerning infant feeding.
Herpes simplex virus types 1 and 2 (HSV-1, HSV-2) cause severe perinatal infections
and, less frequently, prenatal and postnatal infections. Case reports have demonstrated
HSV infections in infants related to maternal HSV-positive breast lesions and inoculation
of virus from primary gingivostomatitis in the infant to the mother's breast during
breastfeeding [56], [57], [58]. Breastfeeding or use of expressed breast milk in the
absence of breast lesions in the mother, with other signs of active HSV infection,
is appropriate when careful contact precautions are followed, including covering the
lesions, remaining clothed or gowned, and careful handwashing. Maternal treatment
or prophylactic treatment of the infant may be reasonable in certain situations to
decrease shedding, hasten clinical resolution of the lesions, and protect the infant.
Breastfeeding by an HIV1-positive mother increases transmission risk through breast
milk 4% to 22%, in addition to the risk for prenatal and perinatal transmission [59],
[60], [61], [62]. Recent reviews document HIV1 transmission through breast milk [63],
[64]. Many issues related to HIV1 transmission through breast milk are considered,
including the increased risk for transmission with primary HIV1 infection in the mother
during lactation, the health of the HIV1-infected, breastfeeding mother, the presence
of the virus and potentially immunologically protective factors in colostrum and breast
milk, factors that contribute to HIV1 transmission in breast milk, and possible interventions
to prevent or limit HIV1 transmission through breast milk. The avoidance of breastfeeding
in maternal HIV1 infection is an important component of preventing mother-to-child
transmission in the United States and other countries.
In resource-poor situations, where the complete avoidance of breast milk can increase
morbidity and mortality because of poor nutrition or other infections, potential interventions
can limit HIV1 mother-to-child transmission. Some of the potentially effective interventions
include exclusive breastfeeding, early weaning, education and support to decrease
the occurrence of mastitis or nipple lesions, antiretroviral therapy for the mother
or infant, treating the human milk to decrease the viral burden (ultraviolet light,
freezing, and thawing), and stimulating the infant's immune defenses with active or
passive immunization. These interventions need to be tested for feasibility, cultural
acceptability, preservation of nutritional benefit, and efficacy where they may have
the greatest effect. Avoidance of breastfeeding by HIV-positive mothers should continue
in countries where an alternative source of nutrition can be provided easily. The
World Health Organization, United Nations International Children's Fund, and the Joint
United Nations Programme on HIV/AIDS recommend counseling, education, and support
for HIV-infected mothers in resource-poor settings where breastfeeding is the norm,
and offer vital nutritional and infection-protective effects so they can make an educated
decision concerning infant feeding. Mothers making either choice should be provided
continuing education, support, and medical care to optimize their infant's and their
own health and to minimize the risk of HIV1 mother-to-child transmission.
HIV2 causes clinical disease similar to infection with HIV1, but with a significantly
slower progression to immune suppression. Ekpini and colleagues [62] documented infrequent
HIV2 vertical transmission, but no cases of late postnatal seroconversion in a cohort
of West African mothers and infants (138 HIV1-positive mothers, 132 HIV2-positive
women, 69 women seropositive for HIV1 and HIV2, and 274 HIV-seronegative women). HIV2
transmission through breast milk is less common than for HIV1, but the risk and possible
factors contributing to transmission have not been quantified adequately. Until additional
data are available concerning HIV2 and breast milk, it is appropriate to follow the
current guidelines for breastfeeding and breast milk related to HIV1 infection.
HTLV-I causes adult T-cell leukemia/lymphoma (ATL), a chronic, progressive neuropathy
called HTLV-I associated myelopathy or tropical spastic paraparesis associated with
various other chronic conditions (uveitis, arthritis, Sjögren's syndrome, infective
dermatitis, and a persistent lymphadenitis in children). Early life infection carries
the greatest risk for adult T-cell leukemia [62]. HTLV-I occurs endemically in limited
areas worldwide, including southwest Japan, the Caribbean, South America, and sub-Saharan
Africa [65], [66]. Transmission is through sexual contact, blood and blood products,
and breast milk. Transmission occurs more frequently in breast-fed infants than formula-fed
infants [67], [68], [69], [70], [71], [72]. A longer duration of breastfeeding correlates
with greater risk for HTLV-I transmission to the infant [72], [73], [74]. Transmission
also has been associated with higher maternal provirus levels and a higher HTLV-I
antibody titer [75], [76]. Complete avoidance of breastfeeding is an effective intervention
to prevent mother-to-child transmission [77]. The median time of transmission was
estimated at 11 to 12 months of age [78]. In areas of low prevalence, the likelihood
of a false positive HTLV-I test is high; therefore repeat testing often is indicated.
In a pregnant woman, antibody titer testing and proviral load quantification are appropriate
to estimate the risk for transmission to the infant. The risk for mother-to-child
transmission should be discussed with the mother and parents. When formula is available
readily and culturally acceptable, then avoiding breast milk or recommending early
weaning (before or at 6 months of age) is reasonable to decrease the risk for HTLV-I
transmission to the infant. Providing the infant with frozen/thawed breast milk may
be an acceptable alternative in certain situations, because freezing decreases the
amount of viable virus in breast milk for other viruses (eg, CMV, HIV1).
HTLV-II causes at least two forms of chronic ataxia (spastic or tropical) [79]. An
association has been noted between HTLV II and several other illnesses: arthritis,
glomerulonephritis, myelopathy, T-hairy cell leukemia, and large granulocytic leukemia.
The predominant modes of transmission are intravenous drug use, infected blood and
blood products, and breastfeeding. The frequency of transmission and the contributing
factors to sexual transmission remain uncertain. HTLV-II has been detected in breast
milk [80] and transmission is more frequent in breast-fed than formula-fed infants
[80], [81], [82], [83], [84], [85], [86], [87]. Nyambi and colleagues [85] demonstrated
a correlation between duration of breastfeeding and transmission rate. Given the nature
of HTLV I and II (ie, early infection, late onset, progressive disease, and no available
therapy), it is appropriate to emphasize prevention. In mothers with documented HTLV-II
infection, it is reasonable to recommend avoiding breastfeeding or limiting its duration
whenever alternative nutrition is available, practical, and culturally acceptable.
Human parvovirus B19 can cause a wide range of clinical illness, but most frequently
causes asymptomatic infection or erythema infectiosum. Severe disease is seen most
often in individuals with hemoglobinopathy, red blood cell abnormalities, and immune
deficiency, and in the fetus or neonate as a result of maternal infection during pregnancy.
Transmission is through contact with respiratory secretions (droplets, saliva) and
less commonly other body fluids (blood and urine). Seroprevalence data show peak parvovirus
infection occurring in school-age children. There is no evidence for parvovirus transmission
through breast milk in humans, although it has been identified in rat milk. Continued
breastfeeding by a mother with parvovirus infection is reasonable.
Respiratory syncytial virus (RSV) is a frequent cause of respiratory disease (upper
and lower tract) in infants and children. In adults, it primarily causes a mild upper
respiratory tract infection. There is no evidence of congenital or perinatal infections.
Neonates acquire the virus postnatally through droplets or direct contact, often leading
to severe disease (bronchiolitis, pneumonia, apnea). Premature infants and neonates
with underlying respiratory disease (hyaline membrane disease, bronchopulmonary dysplasia)
or pulmonary hypertension associated with cardiac disease have greater morbidity and
mortality with RSV infection. These at-risk infants should receive prophylaxis with
either palivizumab (Synagis) or RSV immunoglobulin–intravenous, regardless of the
mode of infant feeding. There is no evidence for transmission of RSV through breast
milk. There is considerable debate over the measurable benefit of breastfeeding in
modifying this disease in neonates. Published studies demonstrate conflicting data
about the potential benefit, perhaps because of difficulties controlling for confounding
variables (eg, crowding and smoking) [88], [89], [90]. Breastfeeding with RSV disease
in the mother or the infant can continue as tolerated, and expressed breast milk can
be used if the infant is unable to suckle because of respiratory distress.
Varicella-zoster virus (VZV) infection causes chickenpox as the primary infection
and zoster or shingles as the recurrent or reactivation infection. Congenital infection
can produce distinctive, unilateral malformations of nerve, skin, and other tissues,
but is rare. Perinatal infection can be severe when the mother presents with the rash
of chickenpox between 5 days before delivery and 2 days after delivery. The severity
of the infant's illness may be caused by transmission of the virus to the fetus during
maternal viremia before formation and transfer of adequate antibodies to the infant
in this narrow window. Postnatal transmission occurs through respiratory droplets
and contact or aerosolization of virus from the skin lesions of either varicella or
zoster. VZV DNA and antibody against VZV have been identified in breast milk [91],
[92]. One case of suspected transmission of VZV has been reported without adequate
proof to exclude the more common modes of transmission [92]. If a mother develops
varicella, breast-fed and formula-fed infants are equally at risk from close contact
with her. They should be separated from her and cared for by another individual during
the mother's rash (period of infectivity). Expressed breast milk can be given to the
infant if no skin lesions involve the breasts or as soon as varicella-zoster immunoglobulin
has been given to the infant.
Other infections
Various other organisms are mentioned in discussions of breastfeeding and infection,
a few selected organisms are reviewed here (Table 3)
.
Table 3
Breastfeeding issues for selected maternal infections
Organisma
Predominant modes of transmissionb
Usual timing of infectionc
Evidence for transmission in breast milk
Clinical significanced
Bacillus anthracis (anthrax)
Contact—animals, animal products, cutaneous lesions; airborne
NA
None
BF/BM; cover lesions; medications for therapy and prophylaxisf
Borrelia burgdorferi (Lyme disease)
Arthropod
NA
DNA by PCR; no reports of illness in infants
BF/BM
Candida spp
Contact
Postnatal (colonization, susceptible infants)
Contact with breast, not breast milk
BF/BM
Dengue viruses (1–4)
Mosquito
NA
None
BF/BM
SARS-associated coronavirus
Contact; droplet
NA
None
BF/BM
Toxoplasmosis gondii
Animal-borne; soil, fecal-oral
Congenital
None
BF/BM
Treponema pallidum (syphilis)
Body fluids; blood
Congenital, perinatal
None
Delay BF/BM 24-hr after initiating maternal therapy; empiric treatment of infant
Vaccinia virus (smallpox vaccine)
Contact; possibly airborne
NA
One case report, contact with breast lesion
BF/BMe
Variola virus (smallpox)
Contact; airborne
NA
None
Avoid BF/BM; separation PI
West Nile virus
Mosquito; blood
NA
One case report (no illness in infant)
BF/BM
This is a selected, limited list intended to consider some important organisms that
cause infection in the neonate or infant and possible issues related to breastfeeding
and breast milk.
Abbreviations: BF, breastfeeding; BM, expressed breast milk; NA, not applicable; PCR,
polymerase chain reaction; PI, period of infection; SARS, severe acute respiratory
syndrome.
a
Organisms that cause various clinical illnesses in the infant and the mother; specific
illnesses are too numerous to list.
b
For breastfeeding and non-breastfeeding situations; does not include all possible
or reported modes of transmission (airborne, body fluids, contact, droplet, food-borne).
c
Does not include all possible times of transmission. If “NA,” the timing of infection
is not associated frequently with pregnancy, delivery, or neonates and infants.
d
Notes the appropriateness of breastfeeding or use of breast milk when the mother has
an infection with that specific organism.
f
Refer to reference [99].
e
Refer to the text for more explanation.
Borrelia burgdorferi is the spirochete that causes Lyme disease. Lyme disease is characterized
by multi-organ system involvement (skin, heart, joints, and nervous system) and can
occur in three stages (early localized, early disseminated, and late disease). The
existence, diagnosis, and treatment of chronic Lyme disease remain highly controversial.
B burgdorferi is primarily arthropod-borne and -transmitted. It is transmitted prenatally
uncommonly, even in endemic areas [93], but B burgdorferi as the cause of illness
in the fetus or congenital abnormalities is debated [94], [95], [96]. B burgdorferi
DNA has been reported in breast milk, but there is no evidence for illness in the
infant or transmission of the spirochete to the infant through breast milk [97]. In
spite of the paucity of data, caution may be warranted. With a confirmed diagnosis
of acute Lyme disease in the mother, it is appropriate to discuss the available information
with the mother or parents and to recommend temporarily avoiding breastfeeding and
breast milk for 24 to 48 hours after beginning maternal antibiotic therapy (amoxicillin
[Amoxil, Trimox, and others], penicillin [numerous trade names], or ceftriaxone [Rocephin]).
Candida organisms can cause significant late disease in hospitalized neonates and
readily colonize most infants without producing significant illness. Mucocutaneous
candidal disease is the most common form of illness in infants, causing thrush and
candidal diaper rash. Invasive candidal infection occurs primarily in individuals
with other illnesses, altered immunity, or skin and mucosal barriers, and after use
of broad-spectrum antibiotics. Late-postnatal infection is most common, intrauterine-ascending
infection is rare, and there is no evidence for a syndrome of congenital Candida infection.
Transmission occurs in healthy individuals through direct contact or contact with
vaginal or oral secretions. The mother and infant serve as a ready source of Candida
organisms to recolonize each other, and this is particularly true during breastfeeding.
Thrush or diaper candidiasis in the infant and mastitis or vulvovaginitis in the mother
should prompt simultaneous treatment of the mother and infant, even when illness or
infection is not obvious in the second individual. Many topical and systemic antifungal
agents are recommended in different regimens to treat and eradicate Candida spp in
the breastfeeding mother–infant dyad. Breastfeeding or expressed breast milk is appropriate
during treatment, although occasionally maternal mastitis can be so painful that temporary
cessation of breastfeeding is necessary for comfort. Management of candidal mastitis
requires close adherence to the recommended therapy, careful follow-up, and effective
lactation support.
Toxoplasma gondii is a protozoan that can cause a congenital infection syndrome with
severe central nervous system and ocular sequelae. Postnatal infection is usually
asymptomatic; a nonspecific febrile illness, a mono-like illness, lymphadenopathy,
or an isolated ocular infection can occur. The cat is the definitive host and transmission
is by ingestion of Toxoplasma cysts contaminating raw or undercooked meat or inadvertent
ingestion of oocysts from soil or contaminated foods. Toxoplasma gondii has been transmitted
through milk in animal models, but this has not been demonstrated for human milk [98].
Breastfeeding and expressed breast milk can be used in the face of maternal Toxoplasma
infection during lactation.
Treponema pallidum, a spirochete, causes multi-system disease in stages similar to
Lyme disease. Transmission is through direct sexual contact and contact with open
lesions or secretions from the lesions in the skin and mucous membranes. Congenital
syphilis occurs in the fetus through placentitis and perinatal infection occurs in
the neonate through contact with the spirochete during passage through the birth canal.
Postnatal infection can occur in the infant through contact with open lesions or secretions
in the infected mother or another adult. If syphilitic lesions involve the breast
or nipples, then breastfeeding or using expressed breast milk should be avoided until
the mother has completed treatment and the lesions have healed. There is no evidence
for transmission of Treponema pallidum in breast milk without a breast or nipple lesion.
Potential infections of bioterrorism
Fears of bio-terrorism have exaggerated the importance of various infectious agents
to the point of being considered in the routine differential diagnosis of many human
illnesses. Breastfeeding has not escaped this concern relative to certain infections,
two of which, anthrax and smallpox, are discussed briefly here (see Table 3)
Bacillus anthracis causes zoonotic disease worldwide. Transmission in humans occurs
through contact with animals or their products (eg, wool) and from person to person
by way of cutaneous lesions. Anthrax occurs in three forms: cutaneous, gastrointestinal,
and inhalational. There is no evidence for person-to-person spread of inhalational
anthrax nor is there evidence of transmission through breast milk. Anthrax lesions
of the breast (rare) would necessitate avoiding breastfeeding and breast milk. Contact
and standard precautions are appropriate for anthrax. Anthrax, if used as a biological
weapon with aerosolization or contamination of the local environment with B anthracis
spores, would expose breast-fed and formula-fed infants equally.
The primary issue relative to anthrax and breast milk is antimicrobial therapy or
prophylaxis after presumed exposure. Clinicians should refer to the published recommendations
for treatment and prophylaxis in infants, children, and breastfeeding mothers [99].
The recommendations propose the use of amoxicillin, doxycycline (Vibramycin, Periostat
and others), ciprofloxacin (Cipro), and several other agents for 60 days. Little information
is available on the prolonged use of doxycycline or ciprofloxacin and their possible
effect on infant's teeth and cartilage growth, respectively. Short courses of doxycycline
or ciprofloxacin in breastfeeding mothers are acceptable without concern for the infant
[100]. Depending on the sensitivity testing of the isolated anthrax strain, amoxicillin
or another drug could be used to complete a course of therapy or prophylaxis in a
breastfeeding mother or her infant.
Smallpox (variola virus) is highly contagious because of the ease of person-to-person
spread by way of droplets, aerosolization from the oropharynx, or direct contact with
skin lesions. It also carries a high morbidity and mortality in susceptible populations.
For these reasons, it is a potential agent in biological terrorism. The exposure risk
of a terrorist act leading to widespread aerosolization, contamination of a closed
space, or contamination of the clothes of adults would be the same for breast-fed
and formula-fed infants. The high transmission risk from household contact necessitates
the separation of any infant from a mother with smallpox. Breast milk should be avoided
during the mother's rash because of the possibility of contamination of the milk from
the extensive lesions, even though there is no evidence of transmission of the virus
to the infant through breast milk.
Smallpox vaccine (vaccinia virus) presents a possibility of secondary or tertiary
spread from the vaccination site. Children over 1 year of age can be vaccinated safely
if there is a probable smallpox exposure. The Advisory Committee on Immunization Practices
recommends not vaccinating pregnant or breastfeeding women or children less than 18
years old in pre-event smallpox vaccination programs [101]. One case of tertiary contact
vaccinia in a breastfeeding infant was reported in 2004. The vaccinee in the household
developed an appropriate reaction at the inoculation site and subsequently his wife
developed vesicles on both areolae (secondary contact vaccinia). The breastfeeding
infant later developed lesions on her philtrum, cheek, and tongue. The mother and
infant were observed closely and remained well. Culture and polymerase chain reaction
(PCR) testing identified vaccinia virus in the mother and infant's lesions, but the
breast milk was not tested [102]. Secondary contact vaccinia from smallpox vaccine
is rare, estimated to occur at a rate of 5 to 7 cases per 100,000 vaccinees [103].
Breast-fed and formula-fed infants have the same risk for transmission from close
contact with a vaccinee (eg, household contact, close physical contact, or sleeping
in the same bed). If the mother has secondary contact vaccinia but her breasts are
without lesions, expressed breast milk can be given safely to the infant with the
continuation of all other appropriate household precautions after smallpox vaccination.
Emerging infections
Every year seems to bring a new “emerging infectious disease.” Three that have captured
public attention in the United States are dengue virus, severe acute respiratory syndrome
(SARS), and West Nile virus (WNV).
Dengue viruses (serotypes 1–4) are flaviviruses that cause dengue fever (DF), dengue
hemorrhagic fever (DHF), and dengue shock syndrome (DSS) in infants less than 1 year
of age, but rarely in neonates less than 3 months of age [104]. Prenatal or perinatal
transmission has been reported in 10 instances [105]. Antibody-dependent enhancement,
with the presence of certain concentrations of specific antidengue IgG pre-existing
in the individual's blood against the infecting strain of virus, reportedly causes
more severe disease. There is no evidence for transmission of dengue virus in breast
milk, nor more severe disease in breast-fed infants compared with formula-fed infants.
There has been no documented person-to- person transmission of dengue virus without
a mosquito vector. The mother or infant with dengue disease can continue breastfeeding
as they are able.
SARS, as observed in 2003, is caused by a coronavirus different from previously studied
coronavirus groups [106], [107]. Because the SARS-associated coronavirus was identified
recently, much about it is unknown, including whether it is transmitted through breast
milk. The SARS virus is transmitted primarily by respiratory droplets. In the pediatric
cases reported in the literature, children had mild respiratory illness, although
the severity of the disease in adolescents seemed more similar to that in adults [108],
[109], [110], [111]. Infants born to mothers with confirmed SARS were born prematurely,
presumably because of maternal illness. Two of the five infants described developed
severe abdominal disease (coronavirus has been linked to necrotizing enterocolitis),
although coronavirus was not identified in any of the infants [112]. It is appropriate
to provide expressed breast milk or breastfeed when either the mother or infant has
SARS.
WNV infection leads to approximately one case of severe neurologic disease for every
20 cases of nonspecific febrile illness and every 150 to 300 cases of asymptomatic
infection (seroconversion) it causes. Although the case fatality rate is high in hospitalized
patients or individuals over 70 years of age; children with clinical illness and infants
with infection less than 1 year of age have been reported rarely [113]. Transmission
occurs through mosquito bite, with mosquitoes of the genus Culex being the primary
vectors. Transmission also has been reported during pregnancy [114], [115], through
organ transplant [116], through percutaneous exposure in laboratory workers [117],
and through blood and blood product transfusion [118]. One case of possible WNV transmission
through breastfeeding has been reported [119]. The mother was infected by a blood
transfusion after delivery, became sick 8 days later, and was being hospitalized with
a meningoencephalitis-like illness. The infant was breast-fed from birth through the
second day of the mother's hospitalization. Samples of the mother's cerebrospinal
fluid and breast milk from days 16 and 24 after delivery tested positive for WNV-specific
IgM. The breast milk from day 16 was also positive for WNV-RNA on PCR testing. Live
WNV was not cultured from the breast milk. The infant remained well. Although this
may constitute a case of transmission of WNV through breast milk, the absence of illness
in this infant (and most infants/children), the transient nature of maternal viremia
with WNV, and the rarity of such a transmission event suggest that there is no reason
to avoid breastfeeding or breast milk when a mother is infected with WNV.
Summary
Three viruses (CMV, HIV, and HTLV-I) frequently cause infection or disease as a result
of breast-milk transmission. Reasonable guidelines have been proposed for when and
how to avoid breast milk in the case of maternal infection. For other viruses, prophylactic
immune therapy to protect the infant against all modes of transmission are indicated
(VZV, varicella-zoster immunoglobulin, HAV and immunoglobulin, HBV, and HBIg + HBV
vaccine). In most maternal viral infections, breast milk is not an important mode
of transmission, and continuation of breastfeeding is in the best interest of the
infant and mother (see Table 2, Table 3).
Maternal bacterial infections rarely are complicated by transmission of infection
to their infants through breast milk. In a few situations, temporary cessation of
breastfeeding or the avoidance of breast milk is appropriate for a limited time (24
hours for N gonorrheae, H influenzae, Group B streptococci, and staphylococci and
longer for others including B burgdorferi, T pallidum, and M tuberculosis). In certain
situations, prophylactic or empiric therapy may be advised for the infant (eg, T pallidum,
M tuberculosis, H influenzae) (see Table 1). Antimicrobial use by the mother should
not be a reason not to breastfeed. Alternative regimens that are compatible with breastfeeding
can be chosen to treat the mother effectively.
In most cases of suspected infection in the breastfeeding mother, the delay in seeking
medical care and making the diagnosis means the infant has been exposed already. Stopping
breastfeeding at this time only deprives the infant of the nutritional and potential
immunologic benefits. Breastfeeding or the use of expressed breast milk, even if temporarily
suspended, should be encouraged and supported. Decisions about breast milk and infection
should balance the potential risk compared with the innumerable benefits of breast
milk.