Nipah: The Very Model of a Pandemic
There are two pieces of good news when it comes to Nipah virus. The first is that it’s only ever been observed in humans in five countries. More on the second later.
Nipah virus is a nasty disease to say the least. It was first identified in 1998 in Malaysia, in the area for which it is named. It is a member of the henipavirus genus of paramyxoviruses which also includes Hendra virus (measles is a distant cousin). The first outbreak of Nipah resulted in 265 human cases with 105 dying, a 40 percent mortality rate. Subsequent outbreaks have recorded an average mortality rate of 75 percent.
“The World Health Organization has just listed Nipah virus as one of the ten most important pathogens to monitor and prepare countermeasures to prevent a pandemic,” EcoHealth Alliance Vice President for Science and Outreach Dr. Jon Epstein said. “Importantly, we’ve also been working internationally with local partners for more than 15 years to better understand where and how Nipah virus is likely to cause outbreaks, so we can prevent small outbreaks from spreading globally.”
In humans, Nipah mostly presents with encephalitic symptoms, or, in layman’s terms, symptoms associated with brain swelling: headache, stiff neck, vomiting, dizziness and coma. It is probably most familiar as the inspiration for the 2011 Steven Soderbergh film Contagion. While Nipah has received relatively little media attention stateside, its transmission does demonstrate the importance of approaching pandemic preparedness from a One Health mindset.
Toward the end of the 20th century, Malaysia experienced rapid growth in both its economy and its population. The former was due, in part, to booming lumber and palm oil industries, both of which required significant clearing of natural rainforest in order to make space.
And as the nation became more prosperous, its agricultural practices shifted as well. Family farms slowly grew into commercial ones, as fewer and fewer people raised their own food. Land was cleared there too, in order to make room for the ramped up farming industry. Large-scale pig farms were increasingly common and on the edges of these piggeries, fruit orchards were planted, so as to generate additional income for the farm.
Nipah virus is endemic to fruit bats which live in Southeast Asia. The virus does not affect them, but they carry it and can spread it through their bodily fluids, like saliva or urine. While wild fruit bats are used to searching the forest for wild figs or nectar, an entire orchard is a far easier food supply for them and fresh mangoes are, well, ripe for the picking. On the index farm, the orchards were planted so closely to the pig enclosures that bits of fruit nibbled by the bats fell into the pigs’ pens, a sweet-looking snack which created the perfect opportunity for a bat virus to pass on to pigs and, later, people.
Understanding pandemics–and preventing them–requires an understanding of each step in this chain of events. At EcoHealth Alliance, we are working on the policy level, to encourage smart and strategic land-use change which considers the potential public health implications of tearing down forest. We are also surveilling wildlife in nearly 30 countries to track which pathogens they carry to mitigate risk of spillover. And, of course, we are working on the ground with people, to educate and to encourage behaviors which lessen the odds of disease spillover.
Nipah provides an extraordinary model for studying and preventing pandemics because its spillover resembles the typical emerging disease in that it is of animal origin, endemic to highly populated and highly diverse regions, and its spread is driven mostly by human behavior.
In the case of the 1999 Nipah outbreak, it wasn’t bats who passed Nipah to humans, but the pigs. And that leads to the second piece of good news about Nipah virus: while person-to-person transmission has been observed, it is relatively rare. Nipah has not yet developed the ability to be spread easily like respiratory viruses such as the flu and SARS. It is very difficult, for now, for Nipah to spread very far from the initial point of spillover. But viruses, like all living things, evolve and, for viruses, evolutionary success is being able to spread far and wide.
Our objective is to study and to learn as much as possible about Nipah virus in animals and people, and the types of human activities like agricultural expansion, that can allow it to jump from bats to people, before it becomes a global pandemic. It is our research that stands between you and the next pandemic.