Estimating Nipah virus prevalence in West Bengal, India
When humans are infected with Nipah virus, more than 70% die, making the virus at least as deadly as Ebola. So why haven’t you heard of it?
Human Nipah virus infection is rare, only affecting a few countries in Southeast Asia. Since the virus’ discovery in 1999, Nipah has warranted little attention from the public. However, the World Health Organization believes that Nipah virus’ high fatality rate and ability to mutate easily increases its potential to cause a devastating global pandemic.
Nipah virus is found in large Pteropus fruit bats across Southeast Asia. Most of our information about the virus comes from Bangladesh, where small Nipah virus outbreaks occur 1–2 times each year. Dr. Steve Luby, a Senior Fellow at FSI, originally identified how individuals in Bangladesh were getting the virus from bats — by drinking raw date palm sap. Date palm trees are commonly used to harvest sugary sap in rural Bangladesh and in its neighboring Indian state, West Bengal. While most of the sap is turned into other sugar products like molasses, some of the sap is consumed raw, just after it is harvested by local sap collectors. Nipah virus cannot survive in the molasses but it can live for weeks in the raw sap. Through epidemiological outbreak investigations, Dr. Luby and his team found that a person infected with human Nipah virus is significantly more likely to have consumed raw sap than a person who was not infected. Further, video footage of date palm trees in Bangladesh shows bats visiting the sap collecting sites frequently at night, licking and leaving behind excrement — a perfect pathway for Nipah virus to travel from bats to humans.
While surveillance of Nipah virus in Bangladesh has helped researchers to better understand transmission and incidence of the viral infection within Bangladesh, a gap continues to exist in our knowledge of Nipah virus in several other countries, in which infected fruit bat populations are endemic. The Indian state of West Bengal, because of its cultural similarity and geographical proximity to Bangladesh, is a natural next step in the development of epidemiological Nipah virus research.
On a FSI Small Research grant, I recently visited West Bengal with Dr. Luby to meet with government officials, local funding partners and individuals in rural communities, who are most at risk for Nipah virus infection. Our goal was to establish government approval, begin crafting a research protocol, seek support from the West Bengal epidemiological community and to begin understanding if raw date palm sap consumption behaviors exist in West Bengal villages, similar to Bangladesh. Local and state officials agreed that Nipah virus was a potential issue and that very little research has been done to understand the actual level of risk in the state. We came to an agreement that the project would estimate human Nipah virus infection risk and incidence, enabling the West Bengal Health Department to incorporate Nipah virus into their state disease surveillance infrastructure.
After meeting with state officials and funding support, I travelled to several village communities in eastern West Bengal (on the border with Bangladesh) to interview individuals about raw date palm consumption. The results of these field interviews indicate that West Bengal likely has very similar raw date palm consumption patterns to Bangladesh, confirming that our project has potential to be useful in reducing Nipah virus infection in the region.
Moving forward, our project will survey a select cohort of West Bengal village communities, that both border Bangladesh and have date palm tree populations. We will inquire about date palm tree harvesting and sap consumption, as well as estimating date palm tree and bat presence in each community. Using this information, we plan to estimate the incidence of human Nipah virus infection within West Bengal, using pre-existing human behavior and ecological data from Bangladesh. The project will take place over the following year.
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Written by Carolyn Oliver, Coterm in Epidemiology, FSI Small Research Grant recipient for summer 2017.
