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West Nile Virus

Context:

The Kerala health department is on alert after the death of a 47-year-old from Thrissur due to the West Nile Virus.

  •  Earlier in 2019, a six-year-old boy in Malappuram district had died of the same infection.

Relevance:

GS II- Health

Dimensions of the Article:

  1. About West Nile Virus
  2. Transmission
  3. Symptoms
  4. Detection of WNV

About West Nile Virus

  • The West Nile Virus is a mosquito-borne, single-stranded RNA virus.
  • The virus was first reported in the state in Alappuzha in 2006 and then in Ernakulam in 2011.
  •  According to the WHO, it is “a member of the flavivirus genus and belongs to the Japanese Encephalitis antigenic complex of the family Flaviviridae”.

Transmission

  • Culex species of mosquitoes act as the principal vectors for transmission.
  • It is transmitted by infected mosquitoes between and among humans and animals, including birds, which are the reservoir host of the virus.
  • Mosquitoes become infected when they feed on infected birds, which circulate the virus in their blood for a few days.
  • The virus eventually gets into the mosquito’s salivary glands.
  • During later blood meals (when mosquitoes bite), the virus may be injected into humans and animals, where it can multiply and possibly cause illness.
  • WNV can also spread through blood transfusion, from an infected mother to her child, or through exposure to the virus in laboratories.
  • It is not known to spread by contact with infected humans or animals.
  • According to the US Centre for Disease Control and Prevention (CDC), it does not spread “through eating infected animals, including birds”
  • To date, no human-to-human transmission of WNV through casual contact has been documented.

Symptoms

  • The disease is asymptomatic in 80% of the infected people.
  • The rest develop what is called the West Nile fever or severe West Nile disease.
  • In these 20% cases, the symptoms include fever, headache, fatigue, body aches, nausea, rash, and swollen glands.
  • Severe infection can lead to encephalitis, meningitis, paralysis, and even death.
  • It usually turns fatal in persons with co-morbidities and immuno-compromised persons (such as transplant patients).

Detection of WNV

  • The virus was first isolated in a woman in the West Nile district of Uganda in 1937.
  • It was identified in birds (crows and columbiformes like doves and pigeons) in the Nile delta region in 1953. Before 1997, WNV was not considered pathogenic for birds, but then, a more virulent strain caused the death in Israel of different bird species, presenting signs of encephalitis and paralysis.
  • In 1999, a WMV strain, believed to be one circulating in Israel and Tunisia, reached New York producing a large outbreak that spread across the United States and eventually across the Americas, from Canada to Venezuela.
  • According to the WHO, human infections attributable to WNV have been reported in many countries in the world for over 50 years.
  • WNV outbreak sites are found along major bird migratory routes.
  • Today, the virus is found commonly in Africa, Europe, the Middle East, North America, and West Asia.

-Source: Indian Express


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