Cytomegalovirus (CMV)

Cytomegalovirus (CMV) is one of the Herpes viruses. It is usually harmless and 50-80% of adults are carriers by the time they are 40 years old. CMV can be transmitted in utero and while breastfeeding. Transmission through breastmilk seems to be the reason for the rapid and common acquisition of cytomegalovirus that occurs among breastfed infants. It must be viewed as a form of natural immunization.1 2 Infections that occur from breastfeeding usually do not cause symptoms or disease in the infant and there are no recommendations against breastfeeding.3

When preterm babies acquire CMV postnatally via breastmilk, they are at greater risk than term infants of exhibiting symptoms of the disease. In the extremely low birth weight (birth weight <1500 g) preterm infant, there is a possibility that CMV acquired from human milk may be associated with a late-onset sepsis-like syndrome. However, the value of routinely feeding human milk from seropositive mothers to preterm infants outweighs the risks of clinical disease, especially because no long-term neurodevelopmental abnormalities have been reported. Freezing of milk reduces but does not eliminate CMV. Heat treatment eliminates the viral load from the milk but also affects bioactive factors and nutrients. Fresh mother’s own milk is preferable for routinely feeding all preterm infants.4 5 6 7

While babies who contract CMV from their own CMV+ parent through breastfeeding do not get sick, babies of those who are CMV- and who receive milk from a CMV+ donor are not protected against the virus through existing antibodies and could get sick, especially if they are premature or immuno-compromised. With proper screening, a recipient can avoid donor milk from a CMV+ person if they themselves are negative or they may decide to freeze or pasteurize the milk to avoid contamination if needed and the donor status is unknown.8

How can breastmilk be pasteurized at home?

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  1. Stagno, et al. 1980. Breast Milk and the Risk of Cytomegalovirus Infection ↩︎
  2. Catherine Peckhman. 1989. Cytomegalovirus in the neonate ↩︎
  3. CDC – About Cytomegalovirus (CMV) ↩︎
  4. AAP. 2012. Breastfeeding and the Use of Human Milk ↩︎
  5. Medela. 2012. Research Overview: The Transmission of Cytomegalovirus to Preterm Infants via Breastmilk: Evidence and Issues ↩︎
  6. Freezing at -20ºC/4ºF for 3 days reduces the virus by 99%. Pasteurization at 63°C/145ºF for eight minutes resulted in no viable cytomegalovirus at all. Friis H, Andersen HK. 1982. Rate of inactivation of cytomegalovirus in raw banked milk during storage at -20ºC and pasteurization ↩︎
  7. Dr. John May, et al. 2005. La Trobe Tables ↩︎
  8. Prenatal testing does not screen for this virus. ↩︎