From Hendra to Wuhan: emerging bat-borne viruses in a quarter of century

The Year of Rat is unfortunately dominated by bats due to the COVID-19 outbreak. Although we are not 100% certain that this is a bat virus, all the evidence suggests that there is a high chance that it originated from bats.  This is a “SARS-like event caused be a SARS-like virus” based on the following: 1) the onset of the oubreak is in the Chinese winter (November – December); 2) the major transmission event(s) have a strong epidemiological link to wildlife market; 3) the virus belongs to the same species, SARS relative coronavirus (SARSr-CoV), as SARS-CoV; 4) a bat CoV genome detected in a horseshoe bat (RaTG13) is 96% identical in sequence to 2019-nCoV.
    
In exactly 25 years, we have had multiple zoonotic diseases outbreaks caused by bat-borne viruses or probable bat viruses:  Hendra in Australia (first detected in 1994), Nipah in Malaysia/Singapore (1998/9), SARS outbreak (2002/3), MERS outbreak (2012), large scale Ebola virus outbreak (2014) and the Covid-19 (2019/20).  

We have discovered that the bat’s innnate defense and tolerance responses are better balanced in comparison to other mammals.  On one hand, they have high basal level defense systems (such as DNA damage repair, heat shock, memberane efflux pumps) switched on before encountering danger signals.  On the other hand, they have evolved sophiscated mechnisms to prevent over reaction (such as over inflammation) upon viral infection and other cell stress signals.

It is now well recognized that bats are a special group of mammals execetptionally fit as natural reservoir of many different viruses.  If we don’t change the way we live, farm and eat, it is almost certain that such outbreak will happen again in the not to distant future.