Context: The Kerala government issued an alert in the State against West Nile fever, a mosquito-borne viral infection, after one death and eight cases were reported in recent days.
About West Nile Virus:
- It is a flavivirus associated to the viruses that are also responsible for causing St. Louis encephalitis, Japanese encephalitis, and yellow fever.
- It is a single-stranded RNA virus and is spread by the Culex species of mosquitoes.
- It was first isolated in a woman in the West Nile district of Uganda in 1937. It was identified in birds in the Nile delta region in 1953.
- Along all major bird migratory routes, WNV outbreak sites are found: Africa, Europe, the Middle East, North America, and West Asia.
- No vaccine for WNV is available. Only supportive treatments can be provided to neuroinvasive WNV patients.
Transmission:
- Principal vector is the culex species of mosquitoes.
- Birds act as the reservoir host of the virus.
- Infected mosquitoes transmit WNV between and among humans and animals, including birds.
- WNV can also get transmitted from an infected mother to her child through blood transfusion.
- A very small proportion of human infections have occurred through organ transplant, blood transfusions and breast milk. There is one reported case of transplacental (mother-to-child) WNV transmission.
- No instance of transmission by contact with infected humans or animals has been reported.
- It does not spread ‘through eating infected animals, including birds.
- According to the World Health Organization (WHO), no human-to-human transmission of WNV through casual contact has been reported till date.
Symptoms:
- Symptoms of the infection include high fever, headache, disorientation, stupor, coma, tremors, convulsions, muscle weakness, and paralysis.
- Most of the symptoms are similar to that of Japanese encephalitis.
- However, 80% of the patients need not show any symptoms.
- Severe infection may even cause neurological diseases like West Nile encephalitis or meningitis or West Nile poliomyelitis or acute flaccid paralysis.
- There are reports of WNV-associated Guillain-Barré syndrome and radiculopathy.
- The Flaviviridae are a family of positive, single-stranded, enveloped RNA viruses.
- They are found in arthropods, (primarily ticks and mosquitoes), and can occasionally infect humans.
- Members of this family belong to a single genus, Flavivirus, and cause widespread morbidity and mortality throughout the world.
- Some of the mosquitoes-transmitted viruses include: Yellow Fever, Dengue Fever, Japanese encephalitis, West Nile viruses, and Zika virus.
- Other Flaviviruses are transmitted by ticks and are responsible of encephalitis and haemorrhagic diseases: Kyasanur Forest Disease (KFD) and Alkhurma disease.