West-Nil-Virus
West Nile virus (WNV) is an enveloped RNA virus from the Flaviviridae family and is one of the most widespread flaviviruses. It is globally distributed with centers of distribution in the tropics but also occurs in temperate regions. The spread via migratory birds is particularly important for European areas. In southern Europe, seasonal transmission is established in summer, but wintering in the region is becoming increasingly common due to climate change. Following an initial widespread WNV outbreak in Germany in 2018, mosquito-borne human cases have also been recorded in Germany since 2019. The virus mainly infects birds, but can also be transmitted to humans, horses and other mammals.
The virus is transmitted from one host to the next by mosquitoes, with a large number of different mosquito species being used. However, mosquitoes, which bite both birds (possible hosts of WNV) and humans, are crucial for the infection of humans.
West-Nil- Virus clinical picture in humans
An infection with WNV is often asymptomatic. About 20% of those infected develop flu-like symptoms (fever, chills, headache and back pain, fatigue and swelling of the lymph nodes). Normally, the symptoms last between three and six days, with the period between infection and the onset of symptoms lasting between two and fourteen days. WNV usually heals without complications and only about one in 100 infected people develop a severe neuroinvasive form of the disease. Approximately 5-10% of patients with neuroinvasive WNV disease die, with older patients with pre-existing cardiovascular disease or immunosuppression being particularly affected. WNV diseases are treated symptomatically, there is no specific antiviral therapy. Isolation of the infected person is not necessary.
West-Nil- Virus clinical picture in horses
Infection is often asymptomatic, with around 20% of infected horses developing clinical symptoms (ataxia, circling, hind hand weakness, tremor, visual disturbances, facial paralysis and other neurological symptoms). 30% of horses with neurological symptoms die.
Souces:
Robert-Koch-Institut
Friedrich-Löffler-Institut
European Centre for Disease Prevention and Control