West Nile Fever is a disease caused by the West Nile Virus, which primarily spreads through the bites of infected mosquitoes.
West Nile fever is a disease caused by the West Nile Virus (WNV), a flavivirus related to other mosquito-borne viruses such as Zika virus, dengue virus, Japanese encephalitis, and yellow fever virus. (Creative Commons)
Kerala’s Health Department on Tuesday, 7 May, issued a statewide alert, urging heightened vigilance and immediate action to contain the spread of the West Nile Virus (WNV).
The alert came after the state reported seven cases of West Nile Fever disease and a death.
This was amidst growing concerns over the emergence of infections of the virus in the Thrissur, Malappuram, and Kozhikode districts.
West Nile Fever is a disease caused by the WNV, a flavivirus related to other mosquito-borne viruses such as Zika virus, dengue virus, Japanese encephalitis, and yellow fever virus.
It primarily cycles between birds and mosquitoes, with humans and other mammals serving as incidental hosts.
Mosquitoes become infected with the virus when they feed on infected birds, and then they can transmit the virus to humans and other animals through subsequent bites.
It affects humans, horses, and various bird species. Most infected individuals show few signs of illness, but some may develop severe neurological illness, which can be fatal.
The virus is primarily spread through the bite of infected mosquitoes, with birds acting as the main reservoir.
WNV was first identified in 1937 in the West Nile region of Uganda. It was isolated from the blood of a woman who was suffering from a febrile illness.
Over the following decades, sporadic outbreaks and cases of West Nile Fever were reported in various parts of Africa, the Middle East, and Europe.
The virus gained significant attention in 1999 when it was detected in the United States for the first time. In that year, an outbreak of West Nile virus occurred in New York City, leading to numerous cases of severe neurological disease and several deaths.
The virus is believed to have been introduced in the United States through infected birds or mosquitoes.
Since its introduction to North America, West Nile Virus has become endemic in many parts of the continent, causing seasonal outbreaks during the warmer months.
In India, WNV has been reported sporadically over the years. The first documented case of West Nile virus infection in India occurred in 1956 in the state of Maharashtra.
Since then, cases of West Nile Fever have been reported in various parts of the country, primarily in states with environmental conditions favourable for mosquito-breeding.
India has experienced outbreaks of the West Nile Virus infection with cases reported in different states, including Gujarat, Kerala, Rajasthan, and Tamil Nadu.
These outbreaks have typically occurred during the monsoon and post-monsoon seasons, when mosquito populations are abundant.
The symptoms of WNV infection can vary widely, ranging from mild to severe, and some people may not experience any symptoms at all.
The incubation period, the time between being bitten by an infected mosquito and the onset of symptoms, typically ranges from 2 to 14 days.
Mild symptoms may include:
These mild symptoms may last for a few days to several weeks, and many people recover completely without any long-term complications.
In some cases, particularly in older adults and individuals with weakened immune systems, the West Nile virus can cause severe neurological complications. These can include:
Neuroinvasive disease, which affects the nervous system, such as the brain and spinal cord, can lead to significant long-term disability and even death in some cases.
It’s important to seek medical attention if you experience severe symptoms, especially if you live in or have recently travelled to an area where the West Nile Virus is known to be present.
Prompt medical care can help manage symptoms and complications associated with severe WNV infection.
West Nile Virus is primarily transmitted to humans through the bite of mosquitoes that become infected with the virus by feeding on infected birds, which serve as the primary reservoir hosts for WNV.
Once infected, mosquitoes can transmit the virus to humans and other animals through subsequent bites.
Although mosquito bites are the primary mode of transmission, West Nile Virus can also be transmitted through other routes, although these are less common. These include:
1. Blood transfusion: Rare cases of WNV transmission through blood transfusion have been reported. Blood donors are now screened for WNV to reduce the risk of transfusion-transmitted infections.
2. Organ transplant: Organ transplant recipients may become infected with WNV if the donor organ comes from an infected individual. Organ donors are now screened for WNV to prevent transmission.
3. Mother-to-child transmission: While uncommon, there have been rare cases of WNV transmission from mother to child during pregnancy, childbirth, or breastfeeding.
4. Laboratory exposure: In rare cases, laboratory workers who handle specimens containing West Nile virus may accidentally become infected through needlestick injuries or other occupational exposures.
It’s important to note that WNV is not spread through casual contact such as touching or kissing an infected person, or by touching infected animals. Additionally, there is no evidence to suggest that WNV can be transmitted through consuming contaminated food or water.
Currently, there is no specific antiviral treatment for WNV infection. Most cases of West Nile Fever — the milder form of the disease — do not require specific medical treatment and resolve on their own with supportive care.
Treatment for West Nile Fever typically focuses on relieving symptoms and providing supportive care.
Preventing mosquito bites is the most effective way to reduce the risk of West Nile virus infection.
This includes using insect repellents, wearing long-sleeved clothing and pants, and minimising outdoor activities during peak mosquito activity times, typically at dawn and dusk.
Additionally, efforts to control mosquito populations and eliminate breeding sites can help reduce the risk of WNV transmission in affected areas.
(Edited by Arkadev Ghoshal)
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