As per the media reports, a seven year old boy from Malappuram District of Kerala is suffering from a West Nile Virus (WNV), a mosquito-borne disease, mostly reported in the continental United States.

The Union Ministry of Health and Family Welfare is closely monitoring the situation and extended support to Kerala in prevention and management of West Nile Virus. Currently, there are no reports available for spread of Nile Virus in other parts of the country.

The Health Ministry dispatched a multi-disciplinary Central team from the National Centre for Disease Control (NCDC) to Kerala that includes Dr. Ruchi Jain, RHO Trivandrum; Dr Suneet Kaur, Assitant Director of NCDC; Dr E Rajendran, Entomologist of NCDC Calicut; and Dr Binoy Basu, EIS Officer of NCDC.

The Indian Council of Medical Research (ICMR) has also been alerted for the same.

Key Takeaways

  • West Nile virus is majorly transmitted through the bites of infected mosquitoes
  • Approximately 80 percent of virus infected people not show any symptoms
  • In severe cases, West Nile virus can cause deadly neurological disease in humans
  • The virus can cause severe disease and death in horses
  • Vaccines are available for use in horses but not for humans
  • Birds are the natural hosts of West Nile virus

Source: WHO

West Nile Virus: Transmission Cycle

As per the World Health Organisation (WHO), the West Nile Virus (WNV) is a member of the flavivirus genus and belongs to the family Flaviviridae.

The West Nile Virus is mainly transmitted to human beings by the bite of an infected mosquito.

Birds -> Mosquitos

       —>

Humans, Horses, Mammals

The virus is maintained in nature through mosquito-bird-mosquito transmission cycle. The infected mosquitoes then infect Humans, horses and other mammals.

Mosquitoes catch virus when they feed on infected birds and then they spread the virus to people and other animals by biting them.

A very small proportion of infection transmission occurred through organ transplant, blood transfusions and breast milk. Fortunately, there has been no human-to-human transmission of WNV through casual contact so far.

In a number of cases, as reported, West Nile virus spread through:

• Exposure in a laboratory setting
• Blood transfusion and organ donation
• Mother to baby, during pregnancy or breast feeding


However, the virus, until now, has not spread through:

• Touch
• Coughing and sneezing
• Eating infected birds or animals
• Handling live or dead infected birds

Natural host and dead-end host of WNV

Birds are the natural and reservoir hosts of the WNV.

Horses and humans are “dead-end” hosts. It implies that once they become infected, they do not spread the infection.

Only about 1 out of 150 infected people develop a serious fatal illness affecting the central nervous system.

The serious illness caused by the West Nile Virus is called neuroinvasive disease. It can be Encephalitis (inflammation of the brain) or Meningitis (inflammation of the membranes that surround brain and spinal cord) or West Nile poliomyelitis.

The recovery from severe illness might take several weeks or months and in some cases, the infected ones might not recover completely.

Symptoms, Diagnosis, and Treatment

Symptoms

Most people infected with West Nile virus do not develop any severe symptoms. About 1 in 5 people who are infected with the virus develop fever and other symptoms like headache, body aches, joint pain, vomiting, diarrhea, or rashes.

However, in case of serious illness after contracting the virus, the symptoms include high fever, headache, neck stiffness, coma, disorientation, tremors, fits, muscle weakness, vision loss, numbness and paralysis.

Diagnosis

If one develops any of the symptoms mentioned above, he or she must consult a healthcare provider. The healthcare provider will carry out tests to identify the infection. These tests are:

• IgG antibody sero-conversion in two serial specimen collected at a one week interval by enzyme-linked immunosorbent assay (ELISA)
• IgM antibody capture enzyme-linked immunosorbent assay (ELISA)
• Neutralisation assays
• Viral detection by reverse transcription polymerase chain reaction (RT-PCR) assay
• Virus isolation by cell culture

Treatment

There are no vaccines or medications to prevent and treat the infection. In the initial phase, the healthcare might advise pain relievers to reduce fever and relieve some symptoms.

In severe cases, patients need to be hospitalised to receive incessant treatment through intravenous fluids, pain medication, and nursing care.

How can one prevent infection from West Nile virus?

As the virus is caused by mosquito bite, the most effective way to reduce the risk of the West Nile Virus is to negate the chances of mosquito bites. One can do so in following manner:

• Use insect repellent
• Use of mosquito nets
• Wearing light coloured clothing
• Wear long-sleeved shirts and pants
• Treat clothing and gear
• Take steps to control mosquitoes indoors and outdoors
• Gloves and protective clothing should be worn while handling sick animals

The West Nile Virus outbreaks have been reported in many countries across the World for over 50 years. The virus was first found in a woman in the West Nile district of Uganda in 1937.

One of the major outbreaks of the West Nile Virus was seen in the United States of America (USA) during 1999-2010.  In 1999, the virus was imported in New York through Israel and Tunisia, producing a large and dramatic outbreak in the following years till 2010.

The largest outbreaks occurred in Greece, Israel, Romania, Russia and the USA. The major outbreak sites were on birds migratory routes.

The WNV has been prevalent throughout Africa, parts of Europe, Middle East, North America, West Asia, and Australia.





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