Is Nipah the next Ebola?

Not quite, says Stanford University epidemiologist Stephen Luby, who has studied the disease in Bangladesh, where there have been either outbreaks or sporadic cases almost every year since 2001. The two known Nipah strains currently circulating aren’t all that easy to transmit.

While the mortality rate for those infected can be high, infection is not all that common. Before this latest outbreak, about 300 deaths had been linked to Nipah, most of which occurred in Southeast Asia and Bangladesh. But the actual number could be higher, Luby says, with some cases going untested or unreported. Because the symptoms of Nipah infection are similar to those for other diseases, including encephalitis and the flu, cases may be misdiagnosed. India has only two main diagnostic laboratories, both in the central city of Pune, equipped to confirm Nipah infection. 

“In order for a disease to spread globally, each person has to infect at least more than one person,” Luby says. But a person with Nipah tends to infect either zero or one other person, according to a 2009 study published online by the U.S. Centers for Disease Control and Prevention. By comparison, a person with measles can infect on average 10 others who aren’t vaccinated. And people who caught Ebola during the 2014 outbreak in West Africa tended to pass it on to between one and three others, PLOS Current Outbreaks reported in 2014.

But “anytime the virus is inside a human, it has the opportunity to evolve and adapt to that human-specific environment,” Luby says. The worst-case scenario is a future strain that can transmit more quickly or easily among humans, which is why the WHO and global health experts are urging more research into vaccines and treatments.

“I hope what we learned from the Ebola outbreak, is that if we have the ability to prepare, we should do that,” says Emily Gurley, an infectious disease epidemiologist at the Johns Hopkins Bloomberg School of Public Health in Baltimore

In fact, in response to this latest outbreak, the Coalition for Epidemic Preparedness Innovations (CEPI), a global alliance that formed last year to encourage and finance the development of vaccines, has announced that they will be granting $25 million to two American biotech companies to accelerate work on a Nipah vaccine. Researchers have tested experimental Nipah vaccines on animals, but have yet to conduct clinical trials. 

Are fruit bats the problem?

Having been around for millions of years, bats have probably carried infectious diseases for nearly as long, Gurley says. Several bat species can carry viruses that are deadly to humans, including Ebola, Marburg, SARS and Nipah, without getting sick themselves (SN: 3/9/13, p. 10).

But scientists say that villainizing bats is not the answer. “They’re a crucial part of their ecosystems,” Gurley says. “They are also really important pollinators.”

Several factors have increased the chance of bat-borne viruses being passed humans, including development that has encroached on the bats’ natural habitats. “It used to be that these bats stayed far away from human populations,” Wang says.