India's southern state of Kerala has shut some schools, offices and public transport in a race to stop the spread of the rare and deadly Nipah virus, which has killed two people.

An adult and a child were still infected in hospital, and more than 130 people have been tested for the virus, spread via contact with the bodily fluids of infected bats, pigs or people, a state health official said on Wednesday.

"We are focusing on tracing contacts of infected persons early and isolating anyone with symptoms," said the state's Health Minister Veena George, who told reporters the virus detected in Kerala was the Bangladesh variant, which spreads from human to human with a high mortality rate but has a history of being less infectious.

"Public movement has been restricted in parts of the state to contain the medical crisis," she said.

Two infected people have died since August 30 in the state's fourth outbreak of the virus since 2018, forcing authorities to declare containment zones in at least seven villages in the district of Kozhikode.

Strict isolation rules have been adopted, with medical staff being quarantined after contact with the infected.

The first victim was a small landholder growing bananas and areca nuts in the district's village of Marutonkara, said a government official who retraced the movement of the victim to track down all the people he could have interacted with and the places visited before his health started to deteriorate.

The victim's daughter and brother-in-law, both infected, are in an isolation ward, while other family members and neighbours are being tested.

The second death followed contact in hospital with the first victim, an initial investigation has shown, but the two were not related, said the official, who sought anonymity as he was not authorised to talk to the media.

Three federal teams, including experts from the National Virology Institute, arrived on Wednesday to conduct more tests and to survey the fruit bat population from the isolated villages.

The Nipah virus was first identified in 1999 during an outbreak of illness among pig farmers and others in close contact with the animals in Malaysia and Singapore.

Outbreaks are sporadic and previous infections in South Asia have occurred when people drank date palm sap contaminated with bat excreta.

In Kerala's first Nipah outbreak, 21 of the 23 infected died, while outbreaks in 2019 and 2021 claimed two more lives.

A Reuters investigation in May identified parts of Kerala as among the places most at risk globally for outbreaks of bat viruses.

Extensive deforestation and urbanisation have brought people and wildlife into close contact.