The head of India's apex medical research body today said the mortality rate of those infected with Nipah virus is very high -- between 40 and 70 percent -- compared to the mortality rate in Covid-19, which was 2-3 percent.

The remarks by Indian Council for Medical Research (ICMR) Director General Rajeev Bahl came a day after the southern state of Kerala reported one more confirmed case of Nipah taking the total number to six, reports our New Delhi correspondent.

More than 700 people are on the "suspected list", who may have been infected with the virus, having come into contact with infected patients, officials in the state said.

He said India would procure 20 more doses of monoclonal antibody from Australia for the treatment of Nipah virus infection.

"We got some doses of monoclonal antibody from Australia in 2018. At present, the doses are available for only 10 patients," he added.

According to Bahl, no one in India so far has been administered with the medicine.

"Twenty more doses are being procured. But the medicine needs to be given during the early stage of the infection," the ICMR DG said, adding it can only given as compassionate use medicine.

He said all efforts are on to contain the spread of the virus in Kerala. All patients are contacts of an index patient, he added.

Asked why cases keep surfacing in Kerala, Bahl said, "We do not know. In 2018, we found the outbreak in Kerala was related to bats. We are not sure how the infection passed from bats to humans. The link couldn't be established. Again we are trying to find out this time. It always happens in the rainy season."

He said that globally monoclonal antibody has been given to 14 patients infected with Nipah virus outside India and all of them have survived.

"Only phase 1 trial to establish the safety of the medicine has been done outside. Efficacy trials have not been done. It can only given as compassionate use medicine," he said.