Even as the rising death toll in Kerala due to a rare brain fever triggered panic in the state, the director of National Institute of Virology (NIV), Pune, said that the situation was not alarming. "The Nipah virus has been causing focal outbreaks [sudden occurrence of an epidemic in a relatively limited geographic area] in very rare situations among humans who accidentally come in contact with Nipah virus from infected bats," said Dr D.T. Mourya, director, NIV, Pune.
The institute had confirmed the outbreak on Sunday night after it tested samples from Kerala sent following the deaths of three family members in Changaroth village of Perambra in Kozhikode on Saturday. The NIV had submitted its report to the Secretory, Department of Health Research, who is also the Director General, ICMR, and several "concerned health officials", Mourya said.
As of now, reports from Kerala suggest that as many as 16 people, including a nurse, have died in Kozhikode and Malappuram districts in the last two weeks.
According to the WHO, Nipah virus (NiV) infection is a "newly emerging zoonosis" that causes severe disease in both animals and humans. The natural host of the virus are fruit bats of the Pteropodidae family, Pteropus genus.
However, as Mourya explained, not all Pteropus bats are infected with the Nipah virus. "All Pteropus bats are not infected with the virus. The virus is circulated among bat population at a very low level, without affecting the bats themselves, " he said, terming it as an enzootic [regularly affecting animals in a particular district or at a particular season] phenomenon.
A very small proportion of bats secrete Nipah virus, Mourya said. "It is a rare situation when humans reach very near to bat roosting [the place where the bat lives], come into contact of the infected secretion, and develop the disease. In the past many outbreaks have occurred in the country," he added.
According to the WHO, the viral infection in humans causes a range of symptoms—from asymptomatic infection to acute respiratory syndrome and fatal encephalitis. There is no vaccine for either humans or animals. The primary treatment for infected humans is "intensive supportive care".
Nipah virus was first identified during an outbreak of disease that took place in Kampung Sungai Nipah, Malaysia in 1998. On this occasion, pigs were the intermediate hosts, the WHO said. However, in subsequent NiV outbreaks, there were no intermediate hosts. In Bangladesh in 2004, humans became infected with NiV as a result of consuming date palm sap that had been contaminated by infected fruit bats. Human-to-human transmission has also been documented, including in a hospital setting in India, said the global health body.
Responding to the situation, Union Minister for Health and family welfare, J.P. Nadda said that he had "reviewed the situation" and asked the director, National Centre for Disease Control to visit the district and initiate the "required steps" in consultation with the Kerala government.