Hyderabad: This week we heard two Australians have died from the mosquito-borne Japanese encephalitis virus. The virus has now been detected in four States in that country. Authorities are concerned that more cases would be around the country and have earmarked extra funding to roll out vaccines to those at risk. Who is recommended to […]
Hyderabad: This week we heard two Australians have died from the mosquito-borne Japanese encephalitis virus. The virus has now been detected in four States in that country. Authorities are concerned that more cases would be around the country and have earmarked extra funding to roll out vaccines to those at risk.
Who is recommended to have the vaccine depends on factors including their age, occupation, and location.
What is Japanese encephalitis?
Japanese encephalitis is caused by the Japanese encephalitis virus. It spreads through mosquito bites. It cannot be transmitted from human to human.
Most people will show no symptoms. However, 1% will develop swelling of the brain (encephalitis). Of those who have symptoms, up to 30% will die and a further 50% will have life-long neurological disability. The infection is particularly severe in the elderly or the young.
The virus had previously been found in Southeast Asia, Western Pacific regions, and in Torres Strait. However, because of its spread into new regions further south, last week Japanese encephalitis was designated a communicable disease of national significance.
The first outbreak of encephalitis attributed to JEV was reported in Japan in 1871. Major epidemics have been reported about every ten years. In 1985, JEV was designated under a separate family Flaviviridae, as a member of genus Flavivirus. The genus Flavivirus has been named after the prototype yellow fever virus (from the Latin word flavi,), and is comprised of 70 small, enveloped viruses with single-stranded positive-sense RNA.
Problem in India
In India, epidemics of JE are reported from many parts of the country, and it is considered a major pediatric problem. The first recognition of JE based on serological surveys was in 1955, in Tamil Nadu. Surveys carried out by the National Institute of Virology of Pune indicated that approximately half of the population in Southern India has neutralizing antibodies to the virus. A major outbreak resulting in a 42.6% fatality rate was reported in the Bankura District of West Bengal in 1973. Subsequently, the disease spread to other States. In Uttar Pradesh, the first major JE epidemic occurred in Gorakhpur in 1978, with 1,002 cases and 297 deaths.
Approximately 597,542,000 people in India live in JE-endemic regions, and 1,500 to 4,000 cases are reported every year.
About the vaccines
Currently, seven Japanese encephalitis virus vaccines are licensed for use in humans globally. Some are based on recombinant DNA techniques, others weakened virus, and others inactivated virus. The Japanese encephalitis vaccines first became available in the 1930s. These vaccines can be given to both pregnant women and newborn babies.
The level of immunity from these vaccines varies. A single dose can provide immunity for up to five years. Whereas some require two doses to provide immunity for two years, with some studies suggesting a third booster after 12 months provides longer protection.
These vaccinations come with some side effects. These include redness, pain and mild swelling at the vaccination site. Other side effects include headache, fatigue and muscle pains.
These vaccines vary in the way they are prepared. Also, different strains of the virus are used to make the different vaccines. This can ultimately affect how well they work to prevent disease if there is a change in the current circulating virus strain.
Who can get the vaccine?
Vaccination is currently recommended for high-risk groups, which includes: Laboratory workers who work with the virus; travelers who will spend one month or more in an endemic region; people living or working in the outer islands of the Torres Strait. Also piggery workers are among workers expected to be considered high risk. That’s because Japanese encephalitis virus infects pigs. The virus then enters the mosquito population when they bite pigs, which then later bite humans and spread it to us.
How to protect ourselves even without vaccine?
There are currently no specific treatments for people with Japanese encephalitis. Symptoms are managed with supportive care, including fluids and pain relief. Vaccination is one form of protection. However, the most useful protection comes from not being bitten by a mosquito in the first place.
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