- A coronavirus outbreak that originated in Wuhan, China, has killed at least 630 people and infected more than 31,500 across 26 countries.
- Coronaviruses are zoonotic diseases, meaning they jump from animals to humans.
- The Wuhan coronavirus originated in bats. One group of researchers says bats may have passed the virus to pangolins, which then passed it to humans.
- The SARS coronavirus, which killed 774 people in the early 2000s, jumped from bats to civets, then to people.
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Genetic research has all but confirmed that the new coronavirus spreading in China — called nCoV-2019 — originally came from bats.
But experts are still racing to pin down another key piece of the zoonotic puzzle: which animal species served as the virus' intermediary between bats and people.
Many possibilities have been floated, including snakes (which is unlikely), pigs, and a weasel-like animal called a civet that passed SARS from bats to people in 2002. Now, a group of researchers from South China Agricultural University in Guangdong suggest the coronavirus' intermediate host might have been the pangolin, an endangered mammal.
According to China's Xinhua news agency, the researchers found that samples of coronaviruses taken from wild pangolins and from infected patients are 99% identical.
But this research has yet to be published or confirmed by other experts.
From pangolins to people?
The novel coronavirus that emerged in Wuhan has so far killed more than 630 people and infected more than 31,500.
Many coronaviruses are zoonotic diseases, meaning they spread to humans from animals. In the case of this one, experts think the virus first infected people at the Huanan Seafood Wholesale Market, where live animals were sold. SARS, which is also a coronavirus, jumped to people at a wet market. too. It originated in bats as well.
At least one species of pangolin can die from coronaviruses, according to a study published last year. That strengthens the theory that the new coronavirus could have jumped from bats to these creatures before making its way into humans.
"I can definitely believe it could be true," Kristian Andersen, an immunologist at Scripps Research, told Nature. "I look forward to the published report and data."
A pangolin resembles a scaly anteater. Its keratin scales are used as ingredients in traditional Chinese medicinal remedies, and its meat is a delicacy in China and Vietnam.
All eight pangolin species are threatened with extinction, according to the International Union for the Conservation of Nature. Pangolins were the most trafficked non-human species in the world in 2013, according to National Geographic; the Convention of International Trade in Endangered Species declared pangolin trade illegal in 2016.
In China, illegal animal trading is punishable by steep fines and jail time. It's not yet clear whether any pangolins (or bats, for that matter) were sold at the Huanan market.
Other possible intermediaries: pigs and civets
A study published Monday in the journal Nature found that the new coronavirus shares 96% of its genetic code with coronaviruses circulating in Chinese bat populations. The research also showed that the virus can dock to a receptor in human cells called ACE2, deep in people's lungs.
That same receptor exists in bats, pigs, and civets, which is why they're the most likely intermediary-species candidates.
A less likely candidate is snakes, despite a January 22 report from scientists who edit the Journal of Medical Virology; they suggested the Chinese cobra could have served as the link. But Michael Skinner, a virologist at Imperial College London, said newer information about the coronavirus genome indicates it's "not really compatible with some of the more exotic hosts that were considered earlier in the epidemic."
The only way to be sure about where the virus came from, however, is to take DNA samples from animals sold at the Huanan market and from bats in the area.
Bats were the original hosts of several other zoonotic diseases
In the past 45 years, at least four pandemics have been traced back to bats. They were the original source of Ebola, which has killed 13,500 people in multiple outbreaks since 1976; Middle Eastern respiratory syndrome, better known as MERS, which can be found in 28 countries; and the Nipah virus, which has a 78% fatality rate.
Researchers traced SARS to a population of horseshoe bats in China's Yunnan province. The virus killed 774 people and infected more than 8,000 in eight months.
"We know a fair amount of viruses on the World Health Organization's Blueprint list of priority diseases have either a direct or indirect link with bats," Vincent Munster, a virologist at Rocky Mountain Kaboratories, previously told Business Insider.
Bats pass along viruses in their poop: If they drop feces onto a piece of fruit that another animal then eats, the creature can become a carrier.
Here's how some of the viruses that have passed from bats to people in the last 50 years compare.
Last March, a study even predicted that bats could be the source of a new coronavirus outbreak in China.
"It is highly likely that future SARS- or MERS-like coronavirus outbreaks will originate from bats, and there is an increased probability that this will occur in China," the researchers wrote.
That's because the majority of coronaviruses can be found in China. Plus, the study authors said, most of the bats that host coronaviruses "live near humans in China, potentially transmitting viruses to humans and livestock."
- Read more about the Wuhan virus:
- Everything we know about the deadly Wuhan virus sweeping across China
- The genetic code of the Wuhan coronavirus shows it's 80% similar to SARS. New research suggests a potential way to neutralize the virus.
- Experts think the Wuhan coronavirus jumped from bats to snakes to people. Bats have been the source of at least 4 pandemics.
- There's a good chance the Wuhan coronavirus will never disappear, experts say. There are only 3 possible endings to this story.
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