As the pandemic's earliest epicenter, the city of Wuhan, China, has been the focus of scientific speculation about the origins of COVID-19.
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Now research has shifted to a broader question -- which animals might have harbored the virus before it jumped to humans.
"So far, that intermediate animal host has not been identified. We know the intermediate for SARS, we know the intermediate for MERS, and it's a big mystery," says Dr. Warner Greene, an investigator at San Francisco's Gladstone Institutes.
Dr. Greene says the COVID-19 virus attaches to a cell receptor found in a wide variety of animals, as well as humans. For a time, suspicions focused on a scaly creature known as a pangolin.
"The pangolin has a very similar virus but it's missing one absolutely key distinguishing feature of SARS Co-V2, so it can't be the pangolin," explains Dr. Greene.
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The most common theories focus on China's bat population, and similar versions of the virus have been detected in bats in southeast Asia. Dr. Shannon Bennett studies disease transmission at the California Academy of Sciences. She says it's critical to know whether a bat might be the direct source, or whether the virus could be passed to a second animal, and jump to humans from there.
"And just understanding the landscape of potential and possible exchanges that could happen with this virus. So preparing for future viruses as well as understanding the intersection between human and non-human animals for this virus," says Dr. Bennett.
The World Health Organization team could use field sampling techniques similar to research groups like the UC Davis One Health Institute. Their experts sample bats in many parts of the world, to better understand the so-called Animal Reservoir of diseases. And experts say with this version of COVID-19 infecting animal populations from minks in Denmark, to gorillas at the San Diego Zoo, understanding its transmission will be vital as the virus mutates and travels.
"So if there's any ongoing transmission from an animal species to humans, you can start looking at animal species that might transmit this to humans to begin with," according to researcher Dr. Arinjay Banerjee of McMaster University.
The World Health Organization team could also use techniques like contact tracing, especially around a food market where a number of early patients were identified. Others have called on China's government to be more transparent about virus work being conducted in a nearby lab at the time of the outbreak.
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