The root of infection is yet to be established
Kerala is yet to resolve the mystery of the origins of the human infection. The fruit bats found in plenty in the Western Ghats are the natural reservoir for the virus, but the root of transmission of the virus to humans remains a hypothesis. It has been assumed that the primary cases might have consumed fruits or palm sap contaminated with NiV, which is present in the urine or saliva of fruit bats. So far, this is only a theory unsupported by evidence. Though bat positivity is consistently traced every year ahead of the outbreak, no intermediary hosts for the virus have been found so dar. In other South Asian countries, the role of intermediaries have been established. The first ever reported outbreak in South Asia that occurred in Malaysia in 1999 and claimed 106, spread from a pig farm. Both animal-to-human and human-to-human transmission has been documented. On the other hand, in the outbreaks in Kerala, while human-to-human transmission has been established, the root of the transmission to the primary case remains unproved. According to Vinod A Narayanan, assistant professor at the department of Biochemistry at Ramachandra Medical College and Research Institute Chennai, the direct transfer of bat viruses to humans is a rare event.