Kerala has reported the first death due to West Nile Fever in the last 3 years, that of a 47-year-old man in Thrissur district, as per media reports. Following this, the state health department has issued directions to destroy mosquito breeding sites in the vicinity, clearing of drains and asked the people to undertake a cleanliness drive in their neighborhoods and remove any collected or stagnant water.

Here are some key facts about West Nile Virus.

• West Nile Virus is a member of the flavivirus genus and belongs to the Japanese encephalitis antigenic complex of the family Flaviviridae.
• The virus was first isolated in the West Nile district of Uganda in 1937; hence its name.
• It is commonly found in Africa, Europe, the Middle East, North America and West Asia.
• The virus is maintained in nature in a cycle involving transmission between birds and mosquitoes. Mosquitoes are the main vectors. Humans, horses and other mammals can be infected. Birds are the natural hosts.
• Transmission: Through the bites from infected Culex mosquitoes. The virus may also be transmitted through contact with other infected animals, blood, or other contaminated tissues. Transmission may also occur through organ transplant, blood transfusions and breast milk. One case of transplacental transmission has been reported. Human-to-human transmission through casual contact has not been reported so far.
• Incubation period: 3-14 days.
• Clinical features: Asymptomatic in 80% cases, while in others, the virus can cause West Nile fever or severe West Nile disease.

o    West Nile fever presents as fever, headache, tiredness, bodyache, nausea/vomiting, skin rash on the trunk (occasionally) and lymphadenopathy. Complete recovery is usual, though symptoms such as fatigue and weakness can persist.

o    Severe West Nile disease or neuroinvasive disease, also called as West Nile encephalitis or meningitis or West Nile poliomyelitis manifests is a potentially fatal illness and manifests as headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. Recovery is prolonged.

• Diagnosis: Detection of IgM antibodies in CSF and serum via IgM antibody capture ELISA, neutralisation assays, viral detection by RT-PCR assay, and virus isolation by cell culture. Anti-IgM can persist for more than a year.
• Treatment: Supportive in severe cases; IV fluids, respiratory support, prevention of secondary infections.
• Prevention: Use of insect repellents, wearing long-sleeved clothing to prevent mosquito bites. Eliminate mosquito breeding sites. Use screens on windows to prevent mosquitoes from entering inside. Educating the general public about the risk factors and the measures to prevent infection. There is no vaccine available for humans.

(Source: West Nile Virus, WHO Fact Sheet, October 2017)