In 2015, study warned of deadly virus
A study published five years ago had warned of viruses similar to that responsible for the Severe Acute Respiratory Syndrome circulating among the Chinese bat population that may pose a serious future threat.
The study was co-authored by Shi Zhengli, a virologist at the Wuhan Institute of Virology, and published in the scientific journal Nature.Last month, Shi published a study linking the origin of the Covid-19 virus to bats. The study published in Nature concluded that 2019-nCoV was 96% identical at the genome level to a bat coronavirus.
The 2015 study had focused on SHC014-CoV, another coronavirus strain which was found to be circulating among the Chinese horseshoe bat populations, but highlighted that recent metagenomic (study of genetic material) studies had identified sequences closely related to the SARS-like viruses in bats which could spill over into outbreaks.
Many scientists and virologists working on animal-to-human transmission of viruses saw the Covid-19 pandemic coming.
For instance, Peter Daszak, a disease ecologist and president of EcoHealth Alliance, a US-based research organisation, wrote in The New York Times that in a World Health Organization meeting in 2018, experts coined the term “disease X,” a virus emerging in animals which would be transmitted to humans and would spread as easily as the flu but with a higher mortality—very similar to Covid-19.
A 2017 study on the diversity of coronaviruses in bats from China found a total of 73 coronaviruses in a sample of 1,067 bats from 21 species in China. Another assessment of why bat viruses are so deadly, conducted by the University of California-Berkeley in February after Covid -9 started spreading, suggested bat cells have a strong immune response, constantly primed to respond to viruses.
High virulence and infectivity wreak havoc when these viruses infect animals with tamer immune systems like humans, the study published in Science Daily concluded. Bats’ ability to fly allows them to pick up pathogens over a vast area.
Several other scientific studies have suggested that land-use change or wild habitat loss are leading to more contact between bats and recipient hosts. “Disrupting bat habitat appears to stress the animals and makes them shed even more virus in their saliva, urine and feces that can infect other animals,” said the Science Daily study.
Researchers working on the ground say the interplay between these factors make virus spillover and an outbreak situation even more likely.
“The relationship between habitat loss and virus spillover from bats is not that simple. There are many areas where we live in close proximity with bats, but there is no spillover. The exceptional thing about bats is that they have the ability to tolerate high viral load without getting sick themselves. In general though, interfaces between bats and people provide opportunities for spillover. We need to study and better understand which particular viruses spill over and cause outbreaks,” said Uma Ramakrishnan, associate professor and senior fellow, Wellcome Trust, National Centre for Biological Sciences.
Rohit Chakravarty, a wildlife biologist at the Indian Bat Conservation Unit, said certain human behaviours made people more vulnerable to Covid-19 like spillovers. “Habitat loss and bushmeat consumption bring humans in closer contact with wildlife. Large commercial wildlife markets that exist in China and Southeast Asia bring humans in contact with live animals that are kept in unsanitary conditions, thereby compounding the risk of disease transmission,” he said.