Breastfeeding and maternal infections

The role of breastmilk in the

prevention of transmission


The West Nile Virus (WNV) and Severe Acute Respiratory Syndrome (SARS) have once again raised suspicions about the safety of infected mothers breastfeeding. Some health care professionals are adopting a "better safe than sorry" attitude, advising infected mothers to stop breastfeeding, despite the fact that there is no evidence that their breastmilk poses a risk to babies. This attitude fails to take into consideration the protective aspects of breastmilk for the baby and relies on the inaccurate assumption that breastmilk and formula are comparable.


Is formula just like breastmilk?


    Formula is only very superficially similar to breastmilk. While formula-fed babies can develop within normal parameters, epidemiological research indicates that they are at higher risk for developing diabetes - both juvenile and adult types - asthma, certain types of cancer, ear and upper respiratory infections, high blood pressure and obesity later in life. Formula fed babies also score lower on cognitive development scores than their breastfed counterparts.


Does stopping breastfeeding decrease the risk of the baby

getting the mother's infection?


    On the contrary, breastmilk contains dozens (if not hundreds) of immune factors that help protect the baby against infection. These include antibodies, white blood cells, factors that deprive bacteria of essential nutrients, fatty acids that attack certain viruses, and complement (a nonspecific immune response to infection). In addition, the damage of infection is due, to a large extent, to the inflammation that accompanies infection. Breastmilk contains several factors that decrease the inflammation of infection. Numerous studies have shown that babies exposed to microbes (viruses, fungi and bacteria) are less likely to get sick if they are being breastfed. In light of this evidence, the question that needs to be asked is why do health professionals persist in telling mothers that they must stop breastfeeding when they have an infection?


Bacteria and viruses in the blood


    In order to get into the milk, a virus or bacterium usually has to be in the mother's blood. Most viral infections do appear in the blood (viraemia), but in almost every case, this occurs before the mother even knows she is sick. Thus, if the mother already has symptoms, the time to stop breastfeeding, even if it were appropriate, has passed.


A mother who has bacteria in her blood is usually very ill, but the majority of bacteria that cause illness in the mother are bacteria to which the baby has already been exposed. The fact that some bacteria may appear in the milk does not increase the risk of the baby becoming ill. If the mother is capable of breastfeeding, she should continue.


Viruses and bacteria can also be spread by droplets (coughing or sneezing) or by touching infected sores. It is important to note that breastfeeding protects the baby against infection, regardless of the source.

The Stress factor

    Stress is another factor that can negatively affect the course of an infection. Removing a baby from the breast is stressful for both mother and baby and is not likely to improve a baby's capacity to fight infection. A baby is comforted, calmed, reassured by breastfeeding. So is the mother.


    An exclusively breastfed baby may refuse to take a bottle if temporarily weaned and run the risk of becoming dehydrated. In these cases, the very real threat of dehydration is infinitely more serious than the minute possibility that the baby will become ill.


West Nile Virus

    The only reported probable case of West Nile Virus (WNV) transmission through breastmilk has prompted many health professionals to advise that mothers sick with WNV should not breastfeed. What was overlooked in this case was that the baby did not get sick but instead developed immunities to the virus.  This is precisely the goal of immunization, and of breastfeeding for that matter. The baby gets the infection, but does not get sick and therefore becomes immune. 


Incidentally, West Nile Virus infection seems to be, as with many other viral illnesses (i.e. chicken pox, polio, hepatitis), less serious in infants and children than in adults.


What about SARS?

    The tremendous fear of  SARS caused many health professionals to immediately advise that infected breastfeeding mothers be separated from their babies. It has not been established that breastfeeding will protect the baby against SARS, but it is likely that those diagnosed with it have been too sick to breastfeed in any case. However, there is no reason to suspect that breastfeeding would not protect the baby against SARS, just as it does against most other infections.


    If the mother is physically capable, she should continue breastfeeding and wear a mask when she is near her baby to decrease the numbers of virus she could transmit. If the mother is merely a contact, then there is no question that she should neither be separated nor advised not to breastfeed.

Thanks to Jack Newman, MD, FRCPC

 Spring 2003 Newsletters Contents