Kozhikode: The source of the Nipah outbreak in Kerala remains a mystery as the virus was undetected in bats captured from the area. The Central and state Animal Welfare Boards had caught bats from the area including the home of Maruthonkara Mohammed Ali, who is considered to be the index case.

Out of the samples collected, 36 were found to be negative. The health department stated that it will continue to test bats and some other animals. Nipah was detected in bats when tests were conducted in the previous years when the disease hit the state. However, how the disease is transmitted from bats to humans remains unclear.

Experts point out that only when clarity is reached regarding the transmission route will preventive measures become foolproof. The widespread death of wild boars in Nipah affected areas had raised concerns and gave rise to the suspicion that this outbreak may have been spread from pigs. 

In Janakikadu, Ottakandam and Charuthippara areas, the death of wild boars in large numbers was noticed by the locals. The carcass of a wild boar found dead in Changaroth Panthirikkara area was examined and samples sent for testing. The health department, though, maintains that there is no abnormality in the death of the pigs.

The first reported outbreak of Nipah in the world was in Malaysia in 1998. It was found that the virus was transmitted from pigs to humans. Studies established that bats transmitted the virus to domesticated pigs.