Officials are looking at the possibility of two killer viruses following the death of a Singapore abattoir worker with symptoms similar to those that affected more than 50 Malaysians said to have died from Japanese encephalitis.
Ling Loo Leng, 49, died in the Singapore General Hospital yesterday.
A second worker from the same abattoir, which has suspended operations, is in hospital with encephalitis-like symptoms.
Singapore, which is a leading buyer of Malaysian pigs, suspended imports from all Malaysian states except Johor, which has been free from the disease, following the workers' illnesses.
The victims of the Malaysian killer virus, which has struck in two states, have been either pig farmers and their employees or residents of villages adjacent to farms.
Japanese encephalitis is usually transmitted from infected pigs or other animals to humans by the culex mosquito.
Unless there are culex mosquitoes in the vicinity of the Singapore abattoir, the worker there seems likely to have been infected by direct contact with the pigs.
A Malaysian official said it was possible the virus was a 'new strain', although the Health Ministry said it was definitely Japanese encephalitis.
Thousands of Malaysians have fled their homes and 11,000 people are being evacuated from the worst-affected villages and farms in Negri Sembilan state.