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.
