West Nile Fever, Type, Transmission, Symptoms, Treatment

Context: The Kerala Government issued an alert in the state against West Nile Fever.

• Kerala is facing an early outbreak of West Nile Fever (WNF) this year, even before the monsoon season.
• With 20 suspected cases and two potential deaths reported, health authorities are on alert.
• The disease, endemic in Kerala for over two decades, often goes underreported due to its asymptomatic nature in 80% of cases.

West Nile Fever in Kerala

• Causative Agent: West Nile Fever is caused by the West Nile virus (WNV), a member of the Flavivirus genus.
• Type: It is a mosquito-borne, single-stranded RNA virus.

Details about West Nile Fever

• Transmission: The virus is primarily spread through bites from infected Culex species mosquitoes.
• • The principal vectors are Culex mosquitoes, which breed in stagnant, large water bodies like paddy fields.
  • WNV circulates in mosquito populations through vertical transmission (adults to eggs).
  • It is not typically contagious between humans, but rare human-to-human transmission can occur via blood transfusion, organ transplant, or from mother to foetus through the placenta.

• Host Range: The virus can replicate in a wide range of hosts including birds, reptiles, amphibians, mammals, mosquitoes, and ticks.
• Geographical Distribution: West Nile virus is found in Africa, Europe, the Middle East, North America, and West Asia.
• Symptoms: Common symptoms include fever, headache, muscle aches, dizziness, and loss of memory.
  • Severe cases, which occur in about 1% of infected individuals, can lead to brain damage, unconsciousness, and sometimes death.
• Cases: The virus was first identified in 1937 in Uganda.
  • The first detection in India occurred in Kerala in 2011.
  • A notable case involved a six-year-old boy from Malappuram, Kerala, who died from the virus in 2019.
• Treatment: There is no specific vaccine available for West Nile virus.
  • Treatment focuses on supportive care, which may include hospitalisation, intravenous fluids, respiratory support, and prevention of secondary infections.
• Diagnostic Challenges and Underreporting: WNF symptoms resemble other mosquito-borne diseases, making diagnosis difficult.
  • The disease is only suspected when patients exhibit signs of neuroinvasive diseases like encephalitis or meningitis.
  • This leads to underreporting, as most cases are recorded as Acute Encephalitis Syndrome (AES).

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