Why the West Nile virus can be life-threatening for some people

The findings could help to identify particularly vulnerable people at an early stage and provide targeted protection in future, as the Geneva University Hospitals (HUG), under whose leadership the study was conducted, announced on Friday.

The West Nile virus is mainly transmitted by mosquitoes and was originally restricted to tropical regions. Due to global warming, it is increasingly spreading in Europe. Last year, Switzerland was infected with the virus for the first time.

Every fifth infected person feels symptoms

In around 80 percent of cases, the infection is asymptomatic. Around 20 percent of those infected develop flu-like symptoms. Only around 0.5 percent develop a serious illness, usually in the form of brain inflammation. This can be fatal or cause severe neurological damage.

For the study now published in the "Journal of Human Immunity", the researchers analyzed data from 13 international patient groups. They found that around 40 percent of patients with severe encephalitis had so-called anti-interferon antibodies circulating in their blood. In contrast, these antibodies could not be detected in people with mild or no symptoms.

New possibilities for prevention

"These people live without knowing that they are vulnerable in an invisible way," study leader Alessandro Borghesi from HUG was quoted as saying in the press release.

According to the researchers, the results open up new possibilities for prevention. For example, people at particular risk - especially those over the age of 65 - could be identified through screening in the future. "This would make it possible to identify people at risk and adapt preventive measures," Borghesi was quoted as saying in the press release.

According to the researchers, the mechanism discovered could also be relevant for understanding severe courses of other viral diseases such as TBE, Covid-19 or influenza.