The virus attacks and destroys the brain and spinal cord. Like most viral illnesses, there is no known cure, and the emphasis is on prevention. As with most tropical and subtropical illnesses, the traveller is often more susceptible than the local population. The disease is transmitted to man by mosquito. The virus commonly infects pigs in rural areas, where biting mosquitoes transfer the infection from pig to person.
Rice is a popular Asian crop and rice paddies provide excellent mosquito breeding grounds.
Areas that combine pig and rice farming are thus more likely to harbour the virus. It is still possible to contract the disease in areas where pigs are not kept however, wild birds also acting as a source of virus. In some regions the disease is a summer illness, in others it occurs throughout the year. The illness is often dramatic in onset, with the sudden appearance of an unremitting fever. Other major symptoms are headache and vomiting.