Health authorities in Kerala have stepped up surveillance and mosquito-control efforts following suspected deaths linked to West Nile fever in Ernakulam district. The alert comes at a time when the state is already battling a rise in Shigella infections, with health officials reporting more than 90 confirmed cases and multiple deaths in recent weeks, prompting heightened disease surveillance across several districts. While the two diseases are unrelated, West Nile fever is a mosquito-borne viral infection, whereas Shigella is a highly contagious bacterial intestinal disease spread through contaminated food, water and poor hygiene. The simultaneous outbreaks have put public health authorities on high alert. Officials have intensified mosquito-control drives, sanitation campaigns, disease monitoring and public awareness efforts to prevent further transmission.

Although West Nile fever is not as widely known as dengue or chikungunya, experts warn that it can occasionally lead to serious neurological complications, particularly among older adults and immunocompromised individuals. Understanding the symptoms, risks and preventive measures is especially important as Kerala navigates multiple infectious disease challenges during the monsoon season.

Kerala Faces Multiple Disease Threats

The West Nile fever alert comes amid growing concern over a separate outbreak of shigellosis, a bacterial infection caused by Shigella bacteria. According to recent reports, Kerala has recorded more than 90 confirmed Shigella cases this month, with clusters reported in districts including Wayanad, Kozhikode, Malappuram and Kannur. Several schoolchildren have been hospitalised, and deaths linked to the infection have also been reported.

Shigella infection typically causes diarrhea, fever, abdominal pain and vomiting and spreads through contaminated food, water and person-to-person contact. West Nile fever, by contrast, spreads through infected mosquito bites and cannot be transmitted through casual human contact.

The dual alerts highlight the importance of both mosquito control measures and strict hygiene practices, particularly during the rainy season when infectious diseases tend to surge. Kerala health authorities have urged residents to eliminate stagnant water, ensure safe drinking water, practise regular handwashing and seek prompt medical care if symptoms develop.

Also Read: Shigella Infection Alert In Kerala: Doctors Explain Who Is Most At Risk

What Is West Nile Fever?

West Nile fever is caused by the West Nile virus (WNV), a member of the flavivirus family, which also includes viruses responsible for dengue, Japanese encephalitis and yellow fever. The virus was first identified in Uganda in 1937 and is now found across Africa, Europe, the Middle East, Asia and the Americas.

Birds serve as the natural hosts of the virus. Mosquitoes become infected after feeding on infected birds and can then transmit the virus to humans and animals through subsequent bites. Humans are considered "dead-end hosts," meaning they generally do not spread the virus further through normal contact.

According to Kerala health officials, the disease does not spread from person to person through casual contact, coughing or sneezing.

What Are The Symptoms?

One reason West Nile fever can be difficult to detect is that most infections cause no symptoms. According to the World Health Organization (WHO), approximately 80% of infected individuals remain asymptomatic. Around 20% develop a mild illness known as West Nile fever.

Common symptoms include:

  • Fever
  • Headache
  • Body aches
  • Fatigue
  • Joint pain
  • Nausea or vomiting
  • Skin rash
  • Swollen lymph nodes

Symptoms usually develop within a few days to two weeks after an infected mosquito bite and often resemble a viral flu-like illness. 

Also Read: Shigella Infection Alert In Kerala: Doctors Explain Who Is Most At Risk

When Can It Become Serious?

While most people recover fully, a small proportion develop severe disease affecting the brain and nervous system. WHO estimates that approximately 1 in 150 infected individuals develops severe neuroinvasive disease.

Warning signs include:

  • High fever
  • Severe headache
  • Neck stiffness
  • Confusion
  • Disorientation
  • Drowsiness
  • Tremors
  • Muscle weakness
  • Seizures
  • Paralysis
  • Loss of consciousness

Kerala health officials have specifically advised people to seek urgent medical care if they experience fever accompanied by neurological symptoms or behavioural changes. Older adults, particularly those above 50 years of age, transplant recipients and individuals with weakened immune systems are at the highest risk of severe disease and complications.

Is There A Treatment Or Vaccine?

Currently, there is no specific antiviral treatment for West Nile virus infection in humans and no licensed human vaccine.

Treatment is primarily supportive and may include:

  • Adequate hydration
  • Rest
  • Fever management
  • Pain relief
  • Hospitalisation in severe cases
  • Intensive care support for neurological complications

Most people with mild illness recover completely, although fatigue and weakness may persist for weeks or even months in some individuals.

Also Read: Climate Change Linked To Rising Antibiotic Resistance In Salmonella: The Lancet

Why Is Mosquito Control So Important?

Since mosquitoes are the primary mode of transmission, controlling mosquito populations remains the most effective strategy for preventing infection. The Kerala Health Department has advised residents to eliminate stagnant water sources and strengthen household mosquito-control practices.

Public health experts recommend:

  • Emptying containers that collect rainwater
  • Cleaning water storage tanks regularly
  • Covering water containers
  • Removing discarded tyres, cans and buckets
  • Ensuring proper drainage around homes
  • Maintaining clean surroundings

These measures not only help prevent West Nile fever but also reduce the risk of dengue, chikungunya and other mosquito-borne diseases.

How Can You Protect Yourself?

WHO and the US Centers for Disease Control and Prevention recommend the following precautions:

  • Use mosquito repellents approved for skin application.
  • Wear long-sleeved shirts and full-length trousers.
  • Install window and door screens.
  • Sleep under mosquito nets where necessary.
  • Avoid outdoor exposure during peak mosquito activity.
  • Use mosquito coils or vaporisers indoors.
  • Keep surroundings free of stagnant water.

During the monsoon season, when mosquito breeding accelerates, these preventive measures become even more important.

What Does The Kerala Alert Mean?

The recent advisory does not indicate a large outbreak but serves as an important reminder that mosquito-borne diseases remain a public health concern, particularly during the rainy season. Health officials have intensified surveillance and awareness efforts to ensure early detection and prevent further spread.

For most people, West Nile virus infection causes either no symptoms or a mild illness. However, because severe neurological disease can occur in vulnerable individuals, prompt medical attention and effective mosquito control remain critical.

The suspected West Nile fever-related deaths in Kerala have drawn attention to a disease that often flies under the radar. While most infections are mild or symptom-free, the virus can occasionally lead to serious neurological complications, especially among older adults and immunocompromised individuals.

With no specific treatment or vaccine currently available for humans, prevention remains the best defence. Public health experts stress that reducing mosquito breeding sites, preventing mosquito bites and recognising early symptoms can significantly reduce the risk of infection and severe illness.



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