Nationwide hunt for Nipah virus in fruit bats soon

The first scientific analysis of the Kerala outbreak by the Indian Council of Medical Research has come up with the warning of a wider circulation of the virus in other parts of the country.

“We will start the surveillance within a month's time and hope to conclude it in the next 12 months. To be carried out in collaboration with the state forest departments, the exercise will start from West Bengal,” R R Gangakhedkar, a senior scientist at ICMR and one of the key members of the team that investigated the Kerala outbreak told DH.

Before Kerala, the eastern state was the sole Indian site to have witnessed Nipah, and that too twice. The first time, it struck Siliguri in 2001, while the second incident was in 2007 in Nadia district. Taken together, there were 71 cases of infection out of which 50 died.

In May 2018, Kerala government declared Nipah outbreak in two districts. As many as 23 cases were identified, including the index (not laboratory confirmed) case. Eighteen were confirmed Nipah cases, whereas four were probable. Seventeen people died.

In their analysis published in the journal of the Infectious Diseases Society of America, the ICMR scientists claimed Kerala outbreak was distinct from previous such episodes reported from Malaysia, Bangladesh and West Bengal.

The epidemiology of the disease was different as the sub-clinical virus load in the population was low. The mode of transmission was different too.

Earlier studies conducted in 2015 in the North-East had shown the circulation of the virus in fruit bats with 8% positivity. The percentage of Nipah positive bats in Kerala is higher (19%) than data previously reported.

Modus operandi

In the proposed surveillance exercise, Pteropus fruit bats would be captured for sampling. The analysis would be carried out at the National Institute of Virology, Pune. The scientists would look not only for Nipah but other disease-causing pathogens too.

Earlier in July, a NIV team reported discovery of the first reservoir of Nipah virus in the wild in India. They found the virus in Cooch Behar – a district in the northern part of West Bengal – and Dhubri in western Assam after sampling more than 100 fruit bats from the region.

Between January 2001 and January 2013, there were 18 Nipah outbreaks in India and Bangladesh. In three cases, each of the infected persons died and on five occasions, more than 80% infected individuals perished. Only in two outbreaks, the case fatality was less than 40%.