NEW DELHI 3 JULY :The mystery over the Nipah outbreak in Kerala mystery has been solved with fruit bats being identified as the source of the outbreak that killed 17 persons in Kozhikode and Malappuram districts in Kerala, the Indian Council of Medical Research (ICMR) has confirmed.
Bats from Changaroth village in Perambra in Kozhikode, where the first infections and death were reported, tested negative for Nipah virus in May, leaving epidemiologists wondering about the possible source of the zoonotic virus that jumps from bats and pigs to cause human infection.
“Scientists have found conclusive evidence of Nipah virus infection in the fruit bats found in the area,” said J P Nadda, Union health and family welfare minister.
The delay in identifying the zoonotic virus host occurred because the wrong bat species were trapped and tested in May. “The 21 bats trapped and tested were insectivores that do not carry the Nipah virus; 55 bats trapped in the second round included fruit bats, which tested positive for the Nipah virus,” said a scientist at Indian Council of Medical Research, who did not want to be named.
Kerala government declared Kozhikode and Malappuram districts free of the virus on Sunday after no new human cases were reported after June 1. Of the 17 deaths, 14 occurred in Khozikode and three in Malappuram, which led to scores of panicked families abandoning their homes and livestock to move to infection-free districts.
Among the many species of fruit bats found across India, Pteropus giganteus (greater Indian flying fox), Eonycteris spelaea, Cynopterus, Scotophilus kuhlii and Hipposideros larvatus are known to carry Nipah virus.
Low levels of the virus stay in bats without sickening them, with a few sick and stressed bats secreting the virus in their droppings, saliva and other body fluids; the exposure to this leads to infection in humans who then infect other humans.
The virus jumped from bats to pigs to humans in Malaysia in 1998-99, and from bats to humans in Bangladesh and India. Pigs, which were identified as carriers in the Nipah outbreak in Malaysia in 1999 that led to 105 deaths, have been ruled out as a source of the virus in Kerala.
“Timely and coordinated efforts of all stakeholders – health workers, state government, scientists, researchers and Central government — led to timely and successful containment of Nipah virus cases in Kerala,” said Nadda.
In Kerala, containment efforts involved orienting hospitals and health workers on infection prevention and control practices, surveillance and contact tracing, contagion treatment protocols and use of personal protection equipment, and safe burial practices.
Following the outbreak, ICMR is prioritising epidemiological studies and research on virus sequencing, drug sensitivity testing and candidate vaccine strain identification while strengthening its lab network for testing high-hazard pathogens.