Kozhikode, May 26: The death toll due to Nipah rose to 12 in Kerala, with one more person succumbing to the deadly virus here today. The deceased, 75-year-old Kalyani, was undergoing treatment at the Medical college here since May 16, official sources said. Two days ago, 61-year-old V Moosa had died of the virus infection. Two members of his family had died earlier of the virus.

His eldest son had also died, but his samples were not tested.

Lini Puthussery, a nurse who had initially treated members of Moosa's affected family members at Perambra Taluk hospital in the district, also died after being infected by the virus.

About 160 samples were sent for tests to the National Virology Institute (NVI) Pune and 15 cases tested positive, health department sources said. Of the 15 confirmed cases, 12 people have died so far.

With samples of insectivores bats testing negative for the virus, samples of fruit-eating bats are being collected from nearby Perambra, the epicentre of the Nipah virus, to be sent for tests at the National Institute of High-Security Animal Diseases (NIHSAD) in Bhopal.

Experts from NIV and departments of Animal Husbandry and Forest have begun collecting samples which would be sent to NIHSAD, to test for the presence of the virus in the fruit-eating bats, Dr N N Sasi, the Director Animal Husbandry, told PTI.

Earlier, samples of three insectivorous bats caught from an unused well of the Moosa family, which lost three members to the virus, were sent to the Bhopal laboratory along with samples of pigs, goats and cattle in the five km radius of the affected area and all of them tested negative, he said. "We are trying to catch fruit-eating bats from the Perambra region now," Sasi said.

According to an official, the droppings, urine and secretions of the bats would also be sent for testing. A Union Health Ministry advisory has said that the virus, which commonly affects animals such as bats, pigs, dogs, and horses, can spread to humans, causing serious illness.

Spread of the virus to humans may occur after close contact with other Nipah infected people, infected bats, or infected pigs. Meanwhile, the Kerala government has said travellers need to avoid only Kozhikode and Malappuram districts from where the deaths have been reported.

Earlier, the government had issued an advisory, stating that travelling to any part of Kerala was safe. However, if travellers wished to be extra cautious, they may avoid the four districts -- Kozhikode, Malappuram, Wynad and Kannur, it said.

The outbreak of the virus infection, which is a newly emerging zoonosis that causes severe disease in both animals and humans, is suspected to be from an unused well which was infested with bats. The natural host of the virus is believed to be fruit bats of the Pteropodidae family, Pteropus genus.