Zika May Not Be the Only Virus to Harm Fetuses

By: Madison Brunner

Zika may not be the only mosquito-borne virus that can harm fetuses, according to a new study from the Washington University School of Medicine and the University of Pittsburgh School of Medicine. Researchers found that West Nile and Powassan viruses, both in the same family as Zika virus, can spread from an infected pregnant mouse to her fetus, causing brain damage and fetal death.

“When Zika emerged two years ago, it caught everyone by surprise,” said Dr. Carolyn Coyne, associate professor of pediatrics at Pitt. “The Zika outbreak made researchers wonder if there is something unique about the Zika virus with respect to its ability to harm a developing fetus, or if related viruses might also have the same ability.”

Dr. Jonathan Miner, an assistant professor of medicine, and graduate student Derek Platt, both of Washington University School of Medicine, developed mouse models to study the effects of West Nile and Powassan viruses, and two other viruses distantly related to Zika, chikungunya and Mayaro viruses.

They found that Zika-like viruses affected the placentas and fetuses more severely that the viruses unrelated to Zika. West Nile virus had the largest impact on placentas and fetuses – with levels 23- to 1,500-fold higher than those of the other three viruses – in addition to causing the most severe brain damage.

Washington University researchers then wanted to discover if these findings would be consistent in human tissue.

They reached out to Coyne, who is known for her work in immunology studies, for help infecting human placentas with one of the four viruses or Zika. They found that Zika, West Nile and Powassan viruses multiplied in maternal and fetal tissue, including the uterine and fetal membranes, whereas chikungunya and Mayaro viruses did not.

“This shows there may be more flaviviruses than Zika that can harm the fetus, but it’s not meant to cause panic,” said Coyne. “This study proves we need to start closely monitoring these viruses by studying pregnant women in infected areas, paying attention during outbreaks in order to be fully prepared if we have another outbreak with a virus like Zika.”