As early as February, researchers identified animal markets in Wuhan as the coronavirus’ likely place of origin, where they believe it began to infect people and where transmission may also have occurred between animals.
Bats, in particular, were identified as a likely source of the virus.
“Given that there were some bats and live animals in the seafood market, (SARS-CoV-2) may be originated from bats or live animals’ exposure to the materials contaminated with bat droppings in the seafood market or surrounding area,” a February study suggests.
This wouldn’t be out of the ordinary for coronaviruses, which have originated in bats before.
The original SARS, MERS and Ebola outbreaks have all been traced back to bats, and scientists like Michael Letko, an assistant professor of virology at Washington State University, believe understanding bat-borne viruses is essential to preventing another pandemic.
Letko has studied certain types of betacoronaviruses and developed a platform to analyze how and to what effect coronavirus particles in various combinations can infect human cells. His platform, which was ready to go at the beginning of 2020, became particularly useful with the news of a new novel coronavirus outbreak.
Using his platform, Letko was able to identify the exact receptor that SARS-CoV-2 latched onto in order to infiltrate a person’s cells and infect them with the virus.
To gain access and replicate in cells, coronaviruses encode a spike protein that then binds to a cell receptor.
In less than two weeks, Letko and his team published some of the first hard lab results identifying the ACE2 receptor as the one that the virus used to infect humans, a key for those working on developing a vaccine.
“We know different receptors are found in different tissues or cell sites, which helps us understand where it will replicate and helps folks working on vaccine development,” he said.
Little research has been done about bat virus ecology and their ability to harbor and spread various viruses that could be detrimental to humans, which is why Letko plans to keep studying it.
“We know these viruses can circulate in these bats, and you can get recombination with more than one virus infecting cells,” Letko said.
He describes the way these viruses circulate and develop in bats as a sort of roulette, when it comes to whether or not a combination could be deadly if transmission chains lead it to humans.
Before the initial SARS outbreak in 2003, Letko said scientists’ understanding of coronaviruses and their potentially deadly effects on humans was not fully understood.
“Before that, we thought all coronaviruses did was give you a seasonal cold,” he said.
After the 2003 outbreak, sequencing efforts began around the world, and coronaviruses were discovered around the globe. More than 200 Lineage B coronaviruses have been identified, including SARS and SARS-CoV-2, and there are more than 500 Lineage C coronaviruses, including MERS-CoV.
Not all coronaviruses have the capacity to affect human cells, Letko said, but it’s important to know which ones can, as the current pandemic has shown. The whole point of developing the analysis tool, besides saving on costs for sequencing coronaviruses, he said, was to identify “which of these viruses has zoonotic potential or more risk to transfer to humans.”
In a post-SARS world, researchers like Letko knew that an outbreak was not likely to be a one-off event.
The question went from “What are the chances of that happening again?” to “What will the next SARS be for us?” Letko said.
Studying viruses in bats, Letko believes, is crucial to understanding and getting ahead of the next potential pandemic although Letko noted he is only analyzing samples from bats, not actually collecting swabs on bats in his line of work.
So how do coronaviruses get from bats to humans?
While direct bat-to-human transmission is believed to be possible, it is also possible for a bat to transmit the virus to another host first. Letko said there is a strong correlation between urbanization and the transmission of coronaviruses from animals to humans.
“Going after new areas is going to lead us to encroach on other animals we haven’t seen before or, more critically, that our livestock haven’t seen before,” Letko said. “While we’re not in direct contact with bats, our livestock are susceptible to bats.”
The threat of future coronavirus outbreaks is very real, and Letko’s work is just beginning.
Not all solutions have to be on the back-end, however, and bat research could be a way to prevent another pandemic, Letko said. He points to the solution for an outbreak of the Nipah virus in Bangladesh, which was believed to be transmitted from bats to humans via containers they used to collect date palm sap. Bats would urinate in the containers at night and contaminate them. A simple solution, like covering the sap containers at night with lids, could stop the spread of the virus.
Letko plans to continue sequencing coronaviruses through his platform in the coming months.
“The point is to expand on the work we did in January and February with different groups of viruses,” he said. “But there are other functions of these viruses that we know of that we want to test in a similar fashion to get big global pictures of how coronaviruses work, so when we discover new ones we don’t have to run to the lab to determine things but (instead) be able to say it looks like this is in that region. So it will be able to do that.”
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