Credit CDC
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Although many people believe that COVID-19 emerged from out of left field, the truth is we've been watching a number of bat borne viruses - including coronaviruses - for decades, fearing a spillover event such as occurred in China in 2019 (see Curr. Opinion Virology: Viruses In Bats & Potential Spillover To Animals And Humans).
High on our list - which also includes Ebola, Hendra, MERS-CoV and SARS-CoV - is the Nipah virus, which has caused sporadic outbreaks in humans - including human-to-human spread - over the past couple of decades.
Carried by fruit bats common to S.E. Asia, in 1998 Nipah sparked an outbreak in Malaysia, which spread first from bat to pigs - and then from pigs to humans - eventually infecting at least 265 people, killing 105 (see Lessons from the Nipah virus outbreak in Malaysia).
Since then, we've seen sporadic outbreaks in Bangladesh and India. Unlike COVID-19 - which appears to kill roughly 1% of those infected, human infection with the Nipah virus is fatal between 70% and 90% of the time.
In the 2013 paper The pandemic potential of Nipah virus by Stephen P. Luby, the author wrote (bolding mine):
Characteristics of Nipah virus that increase its risk of becoming a global pandemic include: humans are already susceptible; many strains are capable of limited person-to-person transmission; as an RNA virus, it has an exceptionally high rate of mutation: and that if a human-adapted strain were to infect communities in South Asia, high population densities and global interconnectedness would rapidly spread the infection.While we've not seen truly large community spread of Nipah, the same could have been said about Ebola prior to 2014, when it was deemed `too lethal to spread efficiently'; until is spread across 3 nations in West Africa killing more than 11,000 people.
Over the past 20 years Nipah, and other bat-borne viruses, have increasingly become viewed as legitimate pandemic threats.
In Steven Soderbergh's 2011 pandemic thriller `Contagion’, technical advisor Ian Lipkin - director of Columbia University’s Center for Infection and Immunity in New York - painstakingly created a fictional MEV-1 pandemic virus based on a mutated Nipah virus.
In Steven Soderbergh's 2011 pandemic thriller `Contagion’, technical advisor Ian Lipkin - director of Columbia University’s Center for Infection and Immunity in New York - painstakingly created a fictional MEV-1 pandemic virus based on a mutated Nipah virus.
- In 2015's Blue Ribbon Study Panel Report on Biodefense a bi-partisan panel described a fictional biological attack on Washington D.C. using a genetically engineered Nipah virus as part of their presentation.
- Two years ago, in the Johns Hopkins Clade X exercise, a genetically altered Nipah virus (spliced onto a parainfluenza backbone) was the cause of their fictional pandemic.
- Also in 2018, in WHO List Of Blueprint Priority Diseases, we saw Nipah and Henipaviral diseases listed among the 8 viral threats in need of urgent accelerated research and development.
Dr. Ian Lipkin is one of the authors of the following report (edited by Dr. Anthony Fauci), published earlier this month in PNAS, that presents evidence from a 6-year EcoHealth Alliance study that shows that (various strains) of Nipah are more widespread in bats than previously believed, and that the risk of a major spillover must be taken seriously.
RESEARCH ARTICLENipah virus dynamics in bats and implications for spillover to humans
Jonathan H. Epstein, Simon J. Anthony, Ariful Islam, A. Marm Kilpatrick, Shahneaz Ali Khan, Maria D. Balkey, Noam Ross,Ina Smith, Carlos Zambrana-Torrelio,Yun Tao, Ausraful Islam, Phenix Lan Quan,Kevin J. Olival, M. Salah Uddin Khan, Emily S. Gurley, M. Jahangir Hossein, Hume E. Field, Mark D. Fielder, Thomas Briese, Mahmudur Rahman, Christopher C. Broder, Gary Crameri, Lin-Fa Wang, eStephen P. Luby, W. Ian Lipkin, and VPeter Daszak
PNAS November 17, 2020 117 (46) 29190-29201; first published November 2, 2020; https://doi.org/10.1073/pnas.2000429117Significance
Nipah virus (NiV) is a zoonotic virus and World Health Organization (WHO) priority pathogen that causes near-annual outbreaks in Bangladesh and India with >75% mortality. This work advances our understanding of transmission of NiV in its natural bat reservoir by analyzing data from a 6-y multidisciplinary study of serology, viral phylogenetics, bat ecology, and immunology. We show that outbreaks in Pteropus bats are driven by increased population density, loss of immunity over time, and viral recrudescence, resulting in multiyear interepizootic periods. Incidence is low, but bats carry NiV across Bangladesh and can shed virus at any time of year, highlighting the importance of routes of transmission to the timing and location of human NiV outbreaks.
Abstract
Nipah virus (NiV) is an emerging bat-borne zoonotic virus that causes near-annual outbreaks of fatal encephalitis in South Asia—one of the most populous regions on Earth. In Bangladesh, infection occurs when people drink date-palm sap contaminated with bat excreta. Outbreaks are sporadic, and the influence of viral dynamics in bats on their temporal and spatial distribution is poorly understood. We analyzed data on host ecology, molecular epidemiology, serological dynamics, and viral genetics to characterize spatiotemporal patterns of NiV dynamics in its wildlife reservoir, Pteropus medius bats, in Bangladesh.
We found that NiV transmission occurred throughout the country and throughout the year. Model results indicated that local transmission dynamics were modulated by density-dependent transmission, acquired immunity that is lost over time, and recrudescence. Increased transmission followed multiyear periods of declining seroprevalence due to bat-population turnover and individual loss of humoral immunity. Individual bats had smaller host ranges than other Pteropus species (spp.), although movement data and the discovery of a Malaysia-clade NiV strain in eastern Bangladesh suggest connectivity with bats east of Bangladesh.
These data suggest that discrete multiannual local epizootics in bat populations contribute to the sporadic nature of NiV outbreaks in South Asia. At the same time, the broad spatial and temporal extent of NiV transmission, including the recent outbreak in Kerala, India, highlights the continued risk of spillover to humans wherever they may interact with pteropid bats and the importance of limiting opportunities for spillover throughout Pteropus’s range.(Continue . . . . )
Follow the link to read the full, highly detailed, research report. A less rigorous, but still informative press release from EchoHealth Alliance (below) provides the gist of the findings.
Six-Year Study Indicates Nipah Virus More Widespread than Previously Thought
NEW YORK – November 2, 2020 – In annual outbreaks throughout Bangladesh, Nipah virus kills around 70 percent of the people it infects. The virus, a distant relative of measles, has no vaccine and no proven medical countermeasures. EcoHealth Alliance, a nonprofit working at the intersection of animal, environmental, and human health on a global scale, released Monday the results of a major six-year study to understand how these outbreaks begin and how to prevent them.
Outbreaks typically occur within what is known as the “Nipah belt,” which stretches along Bangladesh’s western border with India. But EcoHealth Alliance scientists found that bats throughout Bangladesh had relatively similar patterns of Nipah virus infection. The research is published in the journal Proceedings of the National Academy of Sciences of the United States of America.
"Nipah circulates regularly in large fruit eating bats throughout many parts of Asia, but human outbreaks can only occur where there is a route of transmission from bats to humans," EcoHealth Alliance Vice President for Science and Outreach Dr. Jonathan Epstein said."The problem is, we don’t have a good handle on where else in the world spillover may be happening, which means we’re likely missing outbreaks. Risk is not so much limited by geography as it is by human behavior. This is a virus that spreads from person to person and is lethal in three quarters of those it infects, which is why we have to pay close attention to it and do what we can to prevent outbreaks."
Nipah outbreaks have been linked to consumption of raw date palm sap, as well as infection through an intermediate host such as domesticated animals such as pigs.
Of eight bat colonies studied across Bangladesh over a period from 2006 to 2012, researchers from EcoHealth Alliance and its partners found Nipah antibodies present in each location. In one bat colony studied continuously for six years, outbreaks in the bats occurred about every two years, about time it takes for bats to lose herd immunity. Outbreaks in bats can lead to human outbreaks, when there is a route of transmission available. Nipah virus, which in humans leads to brain swelling and often leaves patients in a coma, is already identified as one of the World Health Organization’s highest priority pathogens for vaccine development.
"Finding that bats carrying Nipah virus can be infected anywhere and at any time of year means we have to pay closer attention in areas where Nipah outbreaks may not have been previously reported, to make sure we’re not missing small outbreaks that could lead to bigger ones, " Dr. Epstein, the paper’s lead author, said.
The study also found that the strains of Nipah virus that cause human outbreaks reflect the strains carried by local bats, and that there were different strains of Nipah virus in different areas of the country. Genetic differences in the virus may impact disease severity or transmissibility in humans, something Dr. Epstein is currently studying under new funding from the National Institutes of Health.
Outside of India and Bangladesh, previous outbreaks of Nipah have occurred in Malaysia, Singapore, and the Philippines.
While the Nipah outbreaks we've seen have only demonstrated limited human-to-human transmission, each outbreak provides the virus with additional opportunities to better adapt to humans, and potentially increase its threat.
Nipah isn't alone in this category. There are many other zoonotic viruses with pandemic potential, including Lassa Fever, Monkeypox, MERS-CoV, novel flu, and Disease X; the one we don't know about yet.
While it might seem cruel beyond belief for another, possibly even deadlier, virus to emerge in the next few years - the simple truth is - nature doesn't care. Viruses will continue to evolve, and occasionally jump species, because they can.
The only thing we can do is make sure we are far better prepared for the next pandemic than we were for this one. But the clock is ticking.
