Nipah virus: What is the tropical disease killing patients in India and is there a vaccine?

Infection, first discovered in 1998, commonly carried by fruit bats

An outbreak of the Nipah virus is being blamed for the deaths of 10 people, including a nurse, in the southern Indian state of Kerala.

Three of the victims have tested positive for the virus. The results of blood and bodily fluid tests taken from the other seven fatalities are currently being examined in Pune.

An additional 25 people have been hospitalised after displaying symptoms of the infectious disease, with the health secretary, Rajeev Sadanandan, stating that the authorities are currently unable to determine the extent of its spread due to the virus having an incubation period of between four and 18 days.

But what is the Nipah virus and how is it transmitted?

The disease was first identified among pig farmers in Kampung Sungai Nipah, Malaysia, in 1998 and a year later in Singapore and thrives in tropical southern Asia and Australasia.

That first epidemic saw 100 people die and 300 human cases diagnosed in total. More than a million infected pigs were slaughtered and Malaysia's pork trade duly suffered.

It is transmitted to humans by animals and is most commonly carried by the fruit bat, which might infect via an intermediary. In Bangladesh in 2004, a number of people caught the disease after consuming date palm sap contaminated by infected flying-foxes. Mangoes bitten by the bats were found in a Kerala house where three of the most recent victims were found.

Forty-five people died when further cases were found in Siliguri, West Bengal, in 2001 and another five died of Nipah in the same state in 2007.

Nipah effects humans in a range of ways, from asymptomatic infection to acute respiratory syndrome and fatal encephalitis, an inflammation of the brain.

Common symptoms include fever, headaches and drowsiness, which can progress to a coma if untreated after 24 to 28 hours.

There is currently no vaccine for either humans or animals and the virus has an alarming 70 per cent mortality rate.