Kerala Health department issues alert after West Nile fever cases rise

Kerala’s health department has issued a statewide alert after the vector-borne West Nile fever claimed the life of one person in Thrissur and six other confirmed cases were reported in Kozhikode and Malappuram in two days. According to information, Thrissur, Malappuram and Kozhikode are on high alert as several cases have been detected in the districts.

The state health department officials stated that the death due to West Nile fever occurred at Vadanappally in Thrissur, where a 79-year-old male patient was identified as the victim.

The vector-borne disease has been reported in Kerala earlier too. In 2022, a 47-year-old person died of the disease in Thrissur district. It was first detected in Kerala in 2011 and a six-year-old boy from Malappuram died due to the fever in 2019.

The West Nile fever is spread by the Culex species of mosquitoes. It was first detected in 1937 in Uganda. The virus is commonly found in Africa, Europe, the Middle East, North America, and West Asia. Most people infected with the West Nile virus don't experience any symptoms. The virus can cause neurological disease and death in people and the West Nile Virus (WNV) is a member of the flavivirus genus and belongs to the Japanese encephalitis antigenic complex of the family Flaviviridae, states the World Health Organisation.

Human infection is most often the result of bites from infected mosquitoes. 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 the later blood meals (when mosquitoes bite), the virus may be injected into humans and animals, where it can multiply and possibly cause illness. 

A very small proportion of human infections have occurred through organ transplants, blood transfusions and breast milk.

Infection with WNV is either asymptomatic (no symptoms) in around 80 per cent of infected people and 20 per cent of people who become infected with WNV will develop West Nile fever. Symptoms include fever, headache, tiredness, and body aches, nausea, vomiting, occasionally with skin rash (on the trunk of the body) and swollen lymph glands.

Serious illness can occur in people of any age, however, people over the age of 50 and some immunocompromised persons (for example, transplant patients) are at the highest risk for getting severely ill when infected with WNV, states WHO. The incubation period is usually 3 to 14 days.

The treatment is supportive for patients with neuro-invasive West Nile virus, often involving hospitalisation, intravenous fluids, respiratory support, and prevention of secondary infections. No vaccine is available for humans.

Kerala health minister Veena George said the disease was reported in Malappuram, Kozhikode and Thrissur districts. All the infected persons have recovered, except one. The infected persons, which included children, are all fine now and back at their homes with no new cases reported from the areas they live in.

The samples of those who exhibited symptoms of the disease and had undergone treatment were sent to the National Institute of Virology in Pune as a routine exercise.