Mosquitoes as vectors

The West Nile virus is on the rise in Europe

Mosquitoes are a common vector.

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The West Nile virus is increasingly spreading in Europe. Urban areas and areas where intensive agriculture is practiced are particularly affected by this development. This pathogen can also be contracted here.

The West Nile virus usually infects birds, but rarely also humans. Carriers are mosquitoes. "However, the risk of contracting West Nile fever in Austria is still low," reassures the Agency for Health and Food Safety (AGES).

"In 2023, a single case was reported in Austria, and the person concerned was most likely infected in Italy," says AGES: "There have also been no human deaths in Austria to date." Around 80 percent of infections in humans usually go unnoticed because they do not cause any symptoms. Almost 20 percent of those affected are afflicted by flu-like symptoms, and seven out of every thousand infected people develop "West Nile virus-associated meningoencephalitis" (inflammation of the brain and meninges, note).

Transmission via jellyfish bites
A team of researchers led by Lu Lu from the University of Edinburgh (Scotland) has traced the history of the development and spread of West Nile virus (WNV) in Europe. The West Nile virus is transmitted through jelly bites. It normally circulates between blood-sucking mosquitoes and birds, which are its "main hosts". However, humans and other mammals, especially horses, can also contract the virus, explains AGES: "However, they represent a dead end for the virus." The virus can no longer get into mosquitoes from humans and horses and therefore cannot be transmitted to other humans or horses.

The West Nile virus

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The West Nile virus has been circulating in Europe since the 1960s, report researchers in the journal "Plos Pathogens".

A particularly high rate of spread has been observed where intensive agriculture is practiced. This is probably due to the fact that bird species that are often infected with the West Nile virus live there. The virus also spreads along the flight paths of migratory birds.

In addition, the virus "tends to be attracted to areas with a high degree of urbanization", the researchers wrote. Due to human changes, there is a strong ecological imbalance, a less balanced mosquito community in terms of species diversity and an increase in "common mosquitoes" (Culex pipiens).

Surveillance is the be-all and end-all
Based on the results of their study, the researchers recommend "improved surveillance for early detection of further spread to areas with intensive agricultural use and habitats of migratory birds". Increased attention should also be paid to urban regions.

According to AGES, a nationwide mosquito monitoring program has already been in place in Austria for several years. In addition, a new monitoring project called "OH SURVector", which is funded by the EU, was launched at the beginning of 2024.

The AGES experts report that 60 traps will be set up across Austria for 24 hours in the first and third week of each month from May to October, primarily in urban areas. This is because this would be an advantageous habitat for the main vector, namely the common mosquito "Culex pipiens".

Unfortunately, there is no preventative vaccine for humans, according to AGES. The simplest way to prevent infection is therefore to avoid mosquito bites.