The WHO has named Nipah as one of the eight priority diseases that could cause an epidemic, alongside Ebola and Zika
The death toll from an outbreak of the rare Nipah virus in southern India jumped to 10 on Tuesday with more than 90 people quarantined to try to stem the spread of the disease, officials said.
With tests from other suspect deaths awaited, authorities in Kerala state have ordered emergency measures to control the virus, which is spread by fruit bats.
Three of the fatalities are members of the same family - dead bats were found in a well at their home. A nurse who treated one of the family has also died, leaving a heart-wrenching note for her family.
"We sent 18 samples for testing. Out of these 12 tested positive. Ten of those who tested positive have died and the remaining two are undergoing treatment," a health official in Kerala's Kozhikode district, the centre of the outbreak, told AFP.
Ninety-four people who have come into contact with those who died have been isolated in their homes.
"They have been quarantined as a precaution," Kerala state health surveillance officer KJ Reena told AFP.
Nipah has killed more than 260 people in Malaysia, Bangladesh and India since 1998 and has a mortality rate of nearly 70%, according to the World Health Organisation.
There is no vaccination for the virus which induces flu-like symptoms that lead to an agonising encephalitis and coma.
The WHO has named Nipah as one of the eight priority diseases that could cause a global epidemic, alongside the likes of Ebola and Zika.
Among the dead in the Kerala outbreak was nursing assistant and mother-of-two Lini Puthussery, who had helped to treat one of the original family suffering from Nipah.
Puthussery died on Monday and was cremated before her family members could bid her a final goodbye because of fears the virus could spread.
In a final note she scribbled in a hospital isolation unit, she urged her husband to take care of the children.
"I don't think I will be able to see you again. Sorry. Please take care of our children," she said.
Kerala state Chief Minister Pinarayi Vijayan said Puthussery's "selfless service will be remembered".
He also said many professionals had expressed their willingness to work in Nipah affected areas. "The government of Kerala welcomes their service," he said on Twitter.
Health authorities across the state were on high alert, setting up medical camps and a control room to tackle the emerging situation.
They have urged residents to take precautions include avoiding eating fruit fallen on the ground and drinking raw date palm sap.
UV Jose, district collector of Kozhikode, said government and private hospitals were working in close coordination.
"Health staff are visiting individual households giving them specific instructions including about eating fruits from outside and other precautions," he told AFP.
Authorities in Goa and Tamil Nadu states, neighbouring Kerala, said they were monitoring the spread of the outbreak.
Nipah first appeared in Malaysia in 1998. It spread to Singapore and more than 100 people were killed. On that occasion, pigs were the virus hosts but they are believed to have caught it from bats.
In India the disease was first reported in 2001 and again six years later, with the two outbreaks claiming 50 lives.
Both times the disease was reported in West Bengal state bordering Bangladesh.
Bangladesh has borne the brunt of the disease in recent years, with more than 100 people dying of Nipah since a first outbreak was reported in 2001. In 2004, humans became infected with Nipah after eating date palm sap contaminated by fruit bats.