West Nile Cases detected in Kerala

west nile virus

West Nile Virus has been detected in Kerala. The Kerala government on Tuesday said that cases of West Nile fever have been reported from three districts in the state – Thrissur, Malappuram and Kozhikode.

GS Paper III (Internal Security & Environment):

Focus on Public Health Issues: If the question asks about emerging public health challenges in India, you could briefly mention WNV as a mosquito-borne viral illness with potential health risks, especially if there have been recent outbreaks in India.

According to the health department, West Nile virus can cause a fatal neurological disease in humans. However, approximately 80 percent of those infected will not show any symptoms.

What is West Nile Disease ?

The West Nile Virus (WNV) is a mosquito-borne, single-stranded RNA virus. It is a flavivirus and is related to the viruses that cause Japanese encephalitis and yellow fever.

Why is it called West Nile Virus?

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 deaths of different bird species in Israel, presenting signs of encephalitis and paralysis.

In 1999, a WMV strain, believed to be one circulating in Israel and Tunisia, reached New York and produced a large outbreak that spread across the United States and eventually across the Americas, from Canada to Venezuela.

WNV outbreak sites occur along major bird migratory routes. Today, mosquitoes commonly carry the virus in Africa, Europe, the Middle East, North America, and West Asia.

West Nile Virus in India

In India, antibodies against WNV were first detected in humans in Mumbai in 1952. Southern, Central, and Western India have shown virus activity since then. Researchers have isolated WNV in India from Culex vishnui mosquitoes in Andhra Pradesh and Tamil Nadu, from Culex quinquefasciatus mosquitoes in Maharashtra, and from humans in Karnataka.

In 2013, researchers isolated the complete genome sequence of WNV from human samples during an acute encephalitis outbreak in Kerala between May and June 2011. Recently, authorities have detected West Nile in Kerala. In 2022, a 47-year-old man died of the fever in Thrissur district.



Figure, Transmission Cycle of West Nile Virus Contributed by Bryan Parker] - StatPearls - NCBI Bookshelf

Culex species of mosquitoes act as the principal vectors for transmission. Infected mosquitoes spread the disease 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. Infected mosquitoes may inject the virus into humans and animals during later blood meals (when mosquitoes bite). It can then multiply and potentially cause illness.

WNV can also spread through blood transfusion, from an infected mother to her child, or through exposure to the virus in laboratories.

Scientists do not know it to spread by contact with infected humans or animals.

According to the US Centers for Disease Control and Prevention (CDC), it does not spread “through eating infected animals, including birds.”

What are the symptoms of West Nile fever?


The disease is asymptomatic in 80% of the infected people. West Nile fever or severe West Nile disease attacks the rest. For them, the symptoms include fever, headache, fatigue, body aches, nausea, rash, and swollen glands.

“Estimates suggest that approximately 1 in 150 persons infected with the West Nile Virus will develop a more severe form of the disease. Recovery from severe illness might take several weeks or months. Some effects to the central nervous system might be permanent,” says the CDC.

Additionally, it usually turns fatal in persons with comorbidities and immuno-compromised persons (such as transplant patients). Japanese Encephalitis has a higher death rate..

What is the treatment for West Nile Virus disease?

No WNV-specific prophylaxis, treatment or vaccine is available.

Moreover, healthcare providers give only supportive treatments to patients with neuroinvasive West Nile Virus. Concurrently, health authorities globally advise for personal protective measures to reduce the risk of mosquito bites, such as using mosquito repellents.

Public health departments are to also ensure larval source reduction, especially at breeding and resting sites for the mosquito vectors.




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