WEST NILE FEVER

West Nile fever is a viral infection transmitted to humans by mosquitoes. The infection often runs its course without any signs of illness. Possible signs of illness include flu-like symptoms and a skin rash. Inflammation of the meninges, brain, or other organs can develop in rare cases.

The pathogen, the West Nile virus, is found in various regions all around the world. The virus has long been transmitted in Southern Europe in summer. Climatic changes mean that sufficiently favorable conditions for the West Nile virus can now also be found in Germany. Since 2019, alongside infections in people returning from travel abroad, there have also been reports of transmission via mosquitoes in Germany. The southern regions of eastern Germany are most notably affected.

In the majority of cases, people infected with the West Nile virus do not develop any signs of illness. In around a fifth of cases, the diseases presents with flu-like symptoms. The onset is usually sudden with fever, shivering, headache and back pain, fatigue, and swelling of the lymph nodes. In addition, a nodular, blotchy skin rash spreading from the trunk to the head and the limbs is observed in around half of these patients. Infections with no complications usually heal with no consequences after three to six days. Symptoms such as fatigue, weakness, and exhaustion may persist for several weeks.

Approximately one out of every 100 people infected develops a severe disorder of the central nervous system (CNS). Meningitis develops in some of those affected. Encephalitis is rarer. In such cases, possible signs of illness include a high fever, stiff neck, muscle weakness, lightheadedness, apraxia (movement disorders), paralysis, convulsions, and impaired vision. Around half of the patients with encephalitis suffer long-term consequences.

Inflammation of other organs such as the heart and liver occurs in isolated cases.

Approximately five to ten percent of infections where the CNS is affected result in death.

The time between infection and the onset of the disease is generally 2–14 days. Infected individuals are not contagious. As the West Nile virus cannot reproduce well in humans, mosquitoes cannot become infected with the virus via a bite and subsequently transmit it to others.

There is a risk of contracting West Nile fever when staying in regions where the virus is found and there are high numbers of active mosquitoes. Southern France, northern Italy, Greece and other regions of the Balkans, Turkey, and the Middle East are frequently affected, further north the high-risk areas include parts of Czechia, Hungary, Slovakia, and Austria. North America, Africa, and Australia are also affected. In Germany, West Nile fever can occur in the summer and fall in the southern regions of eastern Germany in particular.

The elderly and those with immunodeficiency are particularly at risk of developing severe symptoms. The elderly and those with a history of cardiovascular disease or immunodeficiency are most at risk of dying from a severe case of West Nile fever.