Tuesday, January 22, 2019

Curr. Opinion Virology: Viruses In Bats & Potential Spillover To Animals And Humans



Based upon influenza's transmissibility, mutability, and established record of sparking large epidemics, novel flu viruses remain at the top of our pandemic worry list.

But over the past couple of decades outbreaks due to bat-borne pathogens around the world have begun to raise serious red flags.
  • In 1998, the Nipah virus - normally carried by fruit bats common to S.E. Asia - 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).
  • Five years later a coronavirus which has been linked to bats called SARS emerged in China, and spread around the globe, infecting more than 8,000 people (see SARS And Remembrance).
  • In 2012, another coronavirus - dubbed MERS-CoV - emerged in the Middle East, and it too is believed to have originated in bats (see EID Journal: South African Bat Carries Close Relative To MERS-CoV).
  • And if that weren't enough, Ebola and Marburg virus are both believed to be of bat origin as well.
In 2017 researchers from EcoHealth Alliance published a letter in Nature (Host and viral traits predict zoonotic spillover from mammals) providing the first comprehensive analysis of viruses known to infect mammals.

From their website summary: 
The study shows that bats carry a significantly higher proportion of viruses able to infect people than any other group of mammals; and it identifies the species and geographic regions on the planet with the highest number of yet-to-be discovered, or ‘missing’, viruses likely to infect people. This work provides a new way to predict where and how we should work to identify and pre-empt the next potential viral pandemic before it emerges.
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.
All of which brings us to an excellent overview of bat viruses with zoonotic potential, which is published in the February edition of Current Opinion In Virology.

Due to its length, I've only posted a few opening paragraphs. Follow the link to download and read the full article.

Viruses in bats and potential spillover to animals and humans

Under a Creative Commons license
open access

In the last two decades, several high impact zoonotic disease outbreaks have been linked to bat-borne viruses. These include SARS coronavirus, Hendra virus and Nipah virus. In addition, it has been suspected that ebolaviruses and MERS coronavirus are also linked to bats. It is being increasingly accepted that bats are potential reservoirs of a large number of known and unknown viruses, many of which could spillover into animal and human populations. However, our knowledge into basic bat biology and immunology is very limited and we have little understanding of major factors contributing to the risk of bat virus spillover events. Here we provide a brief review of the latest findings in bat viruses and their potential risk of cross-species transmission.


Although there have been significant advances in diagnostics and medical countermeasures during the past century, the risk of cross-species transmission of known and unknown pathogens has emerged as a threat to human and animal populations due to a various factors, including industrialization, intensive farming, urbanization, rapid transportation and climate change [1,2•]. It is generally accepted that approximately 75% of emerging infectious diseases for humans are zoonoses [1,3,4]. The rate of emergence of novel viruses appears to be increasing as a result of both increased spillover from their natural reservoirs and our improved ability in detection [3].

Among the newly emerged and most deadly zoonotic viruses discovered in the past few decades, bat-borne viruses occupy a greater proportion than viruses from any other mammalian order [5••,6••,7,8]. Several studies have now concluded that bats are exceptional in their ability to act as natural reservoir of viruses and they are able to harbour more diverse viruses per animal species [6••,9]. While the underlying biology for this observation is yet to be uncovered, it is certain that we will witness more disease outbreaks from bat-borne viruses in the years to come.

At the present time, it is impossible to predict the risk of spillover potential for the vast number of viruses or viral sequences which have been detected in bats around the world. But it will be a good start to focus on the viruses in the ‘known unknown’ category, that is new or variant strains of bat viruses related to those which have already spilled over into and caused diseases in animals or humans. Although bats are known to also carry DNA viruses, all of the disease-causing and species-jumping bat-viruses are so far limited to RNA viruses.

In this brief review, we will focus on the major RNA virus families harboured by bats that have demonstrated spillover and severe disease-causing potential.
        (Continue . . . . )

All things considered, the past couple of decades have turned out to be busy ones for Chiroptologists. For some more bat-related blogs, you may wish to revisit:

Back To The Bat Cave: More Influenza In Bats

EID Journal: A New Bat-HKU2–like Coronavirus in Swine, China, 2017

Emerg. Microbes & Infect.: Novel Coronaviruses In Least Horseshoe Bats In Southwestern China

SARS-like WIV1-CoV poised for human emergence