Such outbreaks are a concern in a country where hundreds die from infectious diseases.

Officials in a third Indian state were checking on Friday if two people had been infected with the brain-damaging Nipah virus that has killed 12 in southern Kerala, although the government described the outbreak as minor.

Such outbreaks are a concern in a country where hundreds die from infectious diseases each year for lack of vigorous disease tracking systems. There is no vaccine for the virus, carried by fruit bats, and the only treatment is supportive care.

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The virus has not spread beyond Kerala, the government said after investigation by health officials linked the initial deaths to a well colonized by bats whose water the victims had been using.

"The Nipah virus disease is not a major outbreak and is only a local occurrence," the government said in a statement, adding that a team of experts continued to monitor the situation.

Blood samples from two men who showed the flu-like symptoms of the virus were sent for testing, said a health official in Telangana, a state neighboring Kerala.

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"We just sent them as a precaution," said K Shankar, medical superintendent of the Sir Ronald Ross Institute of Tropical and Communicable Diseases in Hyderabad.

Two suspect cases in Karnataka, another state bordering Kerala, proved negative, said a medical official there.

All the confirmed infections have involved people who caught the virus from the first victim while he was being treated, said microbiologist G. Arun Kumar.

Nipah virus has not spread in south India, say officials

"Hospital-acquired infections are a major path of human to human transmission," added Kumar, who heads the Manipal Centre for Virus Research that is testing virus samples.

The virus, spread through contact with bodily fluids, has a mortality rate of about 70 percent.

A global coalition to fight epidemics this week struck a $25-million deal with two U.S. biotech groups to speed work on a vaccine.

A clutch of dead bats discovered on the roof of a school in the northern state of Himachal Pradesh triggered a brief scare, but there are no suspected human infections, said health official Sanjay Sharma.

The finding of dead bats was not an unusual event, said one state forest official.

"This is not unusual, but the department has sent bat samples for tests as a precautionary measure," said the official, Ramesh Kan