Can human milk deactivate Zika virus?

On February 1, 2016 the WHO officially declared the Zika virus a Public Health Emergency of International Concern after microcephaly and other neurological disorders became associated with the latest outbreak of the virus. Fifty-three countries have reported an outbreak since 2015, and the CDC reports that there have been 4973 total cases in the United States.

While the virus itself gives cause for alarm, one of the major fears connected with Zika is its ties with microcephaly and other neurological disorders for infants in utero. Pregnant women with Zika have the chance of giving birth to babies with congenital Zika virus syndrome, which can cause anything from malformation of the head to seizures, to hearing and sight problems. 
 With all the health concerns connected to Zika, as well as the growing number of reported cases in the past year, scientists have been busy researching different aspects of the disease, especially in relation to mothers and infants.

A study recently published in Virus Research took a look into the the presence of Zika virus in human breast milk. 
 Previous studies established that Zika virus is present and active in the breast milk of mothers infected with the virus. Despite the revelation, this past June the WHO recommended that mothers continue breastfeeding. According to the WHO, breast milk’s numerous benefits outweigh the risk of passing Zika to the infant. Researchers from the Virus Research study, including Dr. Stephanie Pfänder, a group member of the Virology and Immunology Department of the University of Bern in Switzerland, wanted to dig deeper into the relationship between the breast milk and the Zika virus within it. To do this, they examined the stability of the Zika virus in breast milk to explain its stability over time and find ways to inactivate the virus to make breast milk even safer for infants.

The scientists infected breast milk from three healthy mothers with different strains of Zika. They then stored the breast milk for a period of several days at 4°C. Within one to three days, depending on the donor, the virus became inactivated and no longer able to infect the baby. Researchers hypothesized that fatty acids within the milk damage the viral envelope protecting the virus.

“During the storage process over several days, free fatty acids are released which act [as an] antiviral against the virus,” Dr. Pfänder said in an email. “With our storage, we mimic the release of free fatty acids artificially, however, the same process happens in the stomach of the infant where free fatty acids are being released upon milk digestion which could then act [as an] antiviral against the virus.”

Although the finding indicates that breast milk will deactivate Zika on its own, the researchers also wanted to determine a quick, relatively cheap method to ensure breast milk is safe. They found that pasteurizing the milk at 63°C for 30 minutes made the virus unable to infect the baby.

“We sometimes hear [from] the critics that our approach is quite artificial, as milk is not routinely stored at 4°C for longer time periods,” Dr. Pfänder said in an email. “We do not suggest that mothers should routinely store their milk samples before feeding the infants. However, if a mother has a suspected or confirmed infection with Zika we provide information of how stable the virus could be in the milk sample and how to inactivate it to prevent a possible transmission to the infant.”

The recent findings could prove very important as more of the world faces the threat of Zika, and could help prevent the spread of the virus.

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