Nipah virus has killed 17 people in the southern Indian state of Kerala. It鈥檚 a relatively small toll, from a virus few have heard of 鈥� and after starting in May, the outbreak now seems under control.
But there has been a collective, worldwide shudder among disease experts. Many consider Nipah the scariest of the 鈥渆merging鈥� viruses causing increased concern since the disastrous Ebola epidemic of 2014. It is one of the World Health Organization鈥檚 eight priority viruses for developing a vaccine.
The Kerala outbreak shows why. Nipah had never been seen there, and it is 2600 kilometres away from any known human outbreaks. The death rate may聽now be higher than the 75 per cent average of outbreaks in Bangladesh 鈥� already pretty high. Worse still, the virus may be learning to fly.
Advertisement
Nipah virus was discovered in a town of that name in Malaysia in 1999, when 105 people died of a mysterious brain inflammation. Research revealed that fruit bats carry the virus without getting sick, and infected pigs by dropping half-eaten fruit into pigpens. People got it from pigs.
Bat beginnings
Then Nipah struck western Bangladesh when people drank palm sap infected by fruit bats. There has been an outbreak there nearly every year since and two in nearby India.
The Bangladesh strain of the virus caused the Kerala outbreak, and seems more worrying. There was almost zero person-to-person transmission in Malaysia and also few cases in which the virus infected lungs, says Daniel Lucey of Georgetown University in Washington DC, but that has changed. 鈥淚n Bangladesh, pneumonia and cough are much more common and there is also some person-to-person transmission.鈥�
That transmission is what matters. To cause an epidemic, each infected person must give the pathogen to more than one other, on average. Nipah reaches only 0.48. But some people appear to infect far more than average, suggesting the virus can up its game.
We don鈥檛 know yet how that happens. But Nipah, like Ebola, usually spreads through bodily fluids 鈥� yet some cases, says Lucey, seem to have spread via airborne droplets. If Nipah evolves to do that more often, it could go epidemic more readily.
The good news is that after the 2014 Ebola outbreak, a shaken global health community launched efforts to catalogue and boost research into treatments for worrying viruses, including Nipah.
The effort meant one cutting-edge treatment, a specific antiviral antibody made in Australia,聽could be sent quickly to Kerala, says Marie-Pierre Preziosi of the WHO. It arrived after the virus had already been contained, but India is keeping it for next time.
And days after India diagnosed the outbreak, the Coalition for Epidemic Preparedness Innovations (CEPI), also set up in the wake of Ebola, to test and produce a Nipah vaccine.
The grant was already planned, and should soon be followed by more, says CEO Richard Hatchett. Nipah, like Ebola, strikes small numbers of poor people unpredictably, so vaccines are hard to test, and there is little economic incentive to develop one. CEPI aims to counter that.
It is a race with the virus. Nipah has been seen in fruit bats in at least 10 countries across Asia and Africa, says Lucey, who fears an urban outbreak that could allow Nipah to adapt to people. A vaccine will come none too soon.
