India's encephalitis outbreak
July 24, 2014
Encephalitis is an inflammation of the brain.
The symptoms include high fever, headache, vomiting, confusion and, in severe cases, seizures, paralysis and coma. The disease can result in brain damage. Children and elderly people are especially at risk of developing a severe form of encephalitis. It is fatal in up to 60 percent of cases.
Most often, the inflammation is caused by a virus, but in rarer instances it can be caused by bacteria. Several kinds of viruses can lead to encephalitis, including rabies, flu, measles, herpes and tick-borne encephalitis.
The current outbreak in India has killed more than 100 people in West Bengal and a further 56 in the state of Assam. Its strand is thought to be Japanese encephalitis, which is transmitted by mosquitoes.
More than 300 other people are infected.
Common but still "alarming"
Japanese encephalitis is common during the monsoon season when mosquitoes breed. The monsoon season started in June.
There have also been outbreaks in southern India and Sri Lanka.
Each year hundreds die across India - mainly children who have yet to acquire partial immunity.
There is a vaccine against Japanese encephalitis. But it is expensive and needs three shots, which public health experts say is unworkable in low-income countries.
And people can still fall ill from other viruses that cause encephalitis.
Outbreaks due to modern farming
In South and Southeast Asia, the situation has worsened since irrigated rice production was intensified and expanded.
Mosquitoes transmitting Japanese encephalitis, which is related to dengue, breed in flooded rice fields.
They normally prefer blood meals from animals and feed on pigs. But when the number of mosquitoes explodes, they bite humans as well.
India's state of West Bengal is the worst affected by this current outbreak. Farmers breed pigs in the state.
The best way to tackle the disease is to reduce the number of mosquitoes.
In West Bengal, health officials say they have ramped up fumigation and they hope to get "the situation under control soon."
In the long-term - to keep Japanese encephalitis cases as low as possible - the World Health organization strongly advises against introducing more pigs into affected countries, even as an alternative income source for rice farmers.
The WHO says 24 countries across Southeast Asia and Western Pacific have endemic Japanese encephalitis transmission, exposing almost half the world's population to the risks of infection. There is no cure.