WashU research shows West Nile, like Zika, may also harm fetuses

West Nile virus
West Nile virus (green) grows in human placenta, where the cells are marked red with blue nuclei. A study has found that viruses related to Zika, such as West Nile, can cross the placenta in mice and cause fetal brain damage and death. (Image: Nitin Arora)

A new study from Washington University School of Medicine in St. Louis suggests Zika may not be unique in its ability to cause miscarriages and birth defects. Two viruses closely related to Zika – West Nile and Powassan – can spread from an infected pregnant mouse to her fetuses, causing brain damage and fetal death.

Zika virus garnered worldwide attention beginning in 2015 when reports of an outbreak surfaced in Brazil. Alarm heightened when researchers linked Zika infection in pregnant women with the risk of bearing babies born with microcephaly, or abnormally small heads.

West Nile infects thousands of people every year in the United States. About 1,000 people a year develop life-threatening brain infections that can cause persistent neurological problems.

Powassan is a rare virus spread by ticks. There are only a few dozen documented cases of disease caused by the virus in the U.S. over the past decade, mostly in the Great Lakes region.

Jonathan Miner, MD, PhD, an assistant professor of medicine and the study’s senior author, helped develop mouse models of Zika virus infection during pregnancy while working in the lab of Michael Diamond, MD, PhD. He stumbled across a few reports in medical literature suggesting that West Nile virus also could be spread from mother to child before birth, causing birth defects.

Miner is also an assistant professor of molecular microbiology and of pathology and immunology.

Miner and graduate student Derek Platt, the study’s first author, decided to find out whether West Nile and a related virus known as Powassan could cause similar brain damage and fetal death. Their data showed that other flaviviruses have the same capacity, at least in mice, to infect and cross the placenta and cause fetal damage.

The researchers can’t say for sure what happens when pregnant women are infected with these viruses. But their findings suggest it’s possible they could pose the same risk to developing fetuses that Zika does.

Additional epidemiologic studies to determine whether West Nile infection can cause miscarriage and brain damage in people may be prompted by their discovery.

Read the full article on the School of Medicine’s website.