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Holy Bat Virus! Genome Hints At Origin Of SARS-Like Virus

Bats harbor many types of coronaviruses and were probably the original source of the new coronavirus that appeared in the Middle East.
Bats harbor many types of coronaviruses and were probably the original source of the new coronavirus that appeared in the Middle East.

On the surface, the new coronavirus detected in the Middle East this month looks quite similar to SARS. It apparently causes severe respiratory problems, and can be lethal.

But with viruses, the devil is in their details — the genetic details.

Dutch virologists have just published the whole genome of the new coronavirus — all 30,118 letters of its code. And, the sequence reveals that the mystery virus is most closely related to coronaviruses that infect bats in Southeast Asia.

In fact, the pathogen is more similar to two bat viruses than it is to the human SARS virus that sent the world into a panic when it infected nearly 8,000 people in 2003.

Virologist Ron Fouchier, who has done controversial work on bird flu viruses, led the sequencing effort of the SARS-like virus. He tells Shots the results suggest that the new coronavirus virus came from bats. "Bats harbor many coronaviruses, so it's logical to assume that bats are the natural reservoir" of the new pathogen, he says.

"But this doesn't mean the Saudi man contracted the virus from bats," says Fouchier.

When viruses jump from animals to humans, there's usually a second animal that connects the natural carrier with humans. This species is called the amplifier because it increases the number of viral particles that can hop over into people.

With SARS, Fouchier says, it probably started off in bats and then jumped into an exotic animal, such as a civet cat, before it made its way to people.

This type of infection trajectory fits with what epidemiologists have seen, so far, for the new coronavirus.

In the past few weeks, John Watson and his team at Britain's Health Protection Agency have tracked down about 60 people who recently came in contact with one of the men infected with the virus. "None of these contacts have become seriously ill or shown any sign of being infected with the virus," Watson tells Shots.

Plus, there's nothing special happening where the sick man lived, such as an uptick in cases of respiratory illnesses. This is strong evidence that the virus came from an animal and that it probably can't yet move between people.

But to know for sure, Watson says, scientists need to find more cases of the new virus.

The genome sequence will be a big help on this front. Fouchier and his team just published a diagnostic test for the new virus, which doctors around the world can use to verify suspected cases of the disease.

Fouchier says that the genome may also give clues to drugs that may be effective against the virus.

Companies can also begin to design vaccines for the virus, Fouchier adds. "There are experimental vaccines for SARS, and these could be updated to work on the virus," he says. "All knowledge that we built for SARS is not lost."

So what's he doing next? First, taking a few steps backward. "We still need proof that the virus is the cause of the disease," he says. "We are currently starting animal experiments with macaques and ferrets to show that this virus actually makes animals sick. Many viruses don't."

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Michaeleen Doucleff, PhD, is a correspondent for NPR's Science Desk. For nearly a decade, she has been reporting for the radio and the web for NPR's global health outlet, Goats and Soda. Doucleff focuses on disease outbreaks, cross-cultural parenting, and women and children's health.
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