West Nile Virus

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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

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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”.

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.

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).

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