West Nile Virus

West Nile virus (WNV) is a so-called Arbovirus. Arboviruses are viruses that are transmitted by arthropods, like flies, ticks, and mosquitos. A BPRC research line focuses on emerging arboviruses transmitted by mosquitos. These mosquito-borne viruses include clinically relevant viruses like Dengue Virus (DENV), Yellow Fever Virus (YFV), Chikungunya virus (CHIKV), Rift Valley Fever virus (RVFV), Japanese encephalitis virus (JEV), and the West Nile virus (WNV).

West Nile virus was first isolated in the West Nile district of Uganda in 1937. Until the 1990-ies, the different genetic variants of WNV were primarily found in Africa, India, and Australia. However, since 1990 the virus has spread to Europe, en in 1990, WNV has crossed the Atlantic Ocean to North America. This has led to a rapid spread across the American continent.

Denv Spread
Global spread of WNV (Weaver and Reisen, 2010)

Birds are the main hosts for West Nile virus. In general, birds will not develop disease symptoms, but can carry enormous amounts of virus in their blood. The virus can than be transmitted by blood-sucking mosquitos to incidental hosts, like humans and other mammals.

In humans, 80% of WNV infections will proceed without any symptoms. In 20% of WNV infections, patients will develop mild flu-like symptoms (‘West Nile fever’), but in few cases (<1%), WNV infection can cause serious disease symptoms, like encephalitis and meningitis (‘West Nile neuro-invasive disease’). In a small number of patients (< 0.1%) WNV infection is lethal, especially in patients with a compromised immune system.


Macaques and common marmosets can be infected with West Nile virus and offer researchers unique insights into the biology and virus-induced pathological events. Additionally, because of their immunological similarity to humans, they are well-accepted animal models for the preclinical evaluation of vaccine candidates or antiviral compounds. The WNV infection model of rhesus macaques has been used at the BPRC to evaluate the immunogenicity and efficacy of West Nile virus vaccines. In a successful study we were able to protect all vaccinated animals against WNV viremia.