Nature Medicine | Spoonful of Medicine

Mysterious new SARS-like coronavirus came from bats

Genetic analysis has confirmed that the cases of SARS-like viral disease that made headlines this fall—first killing a Saudi Arabian man in June and then sickening a Qatari man in September—were the result of a single coronavirus strain that made the leap from bats to humans.

“These two individuals were exposed to the same virus that was harbored in bats in the Saudi Arabian peninsula,” says Ralph Baric, a microbiologist at University of North Carolina–Chapel Hill who was not involved in the work.

A team led by Ron Fouchier, a virologist at the Erasmus Medical Center in the Netherlands, sequenced all 30,000 nucleotides of the new virus’ genome. Reporting today in mBio, the researchers found that the virus is most closely related to two coronaviruses found in bats, one from vesper bats and another from pipstrelle bats. The finding mirrors earlier discoveries that bats often serve as reservoirs and likely sources of coronaviruses for people. It also validates preliminary molecular details reported earlier this month in the New England Journal of Medicine.

In unpublished material disclosed in a press release to accompany the mBio paper, Fouchier and his colleagues additionally found that the isolates from the first two men infected with the virus differed by only 99 nucleotides, indicating that the two viruses are the same species. Genetic data from a third viral isolate taken from another Saudi Arabian man who earlier this month came down with what scientists think is the same coronavirus  are not yet available.

It could be worse

Although it’s still too early to make definitive statements, Baric says that the novel coronavirus—dubbed HCoV EMC/2012—does not appear to be transmissible between people, which distinguishes it from the virus responsible for severe acute respiratory syndrome (SARS) that spread between thousands of people a decade ago, killing around 10% of those infected. “If it were as transmissible as SARS, it would be much more dangerous,” he says.

Baric and his team have created a new vaccine strategy, described earlier this month in Nature Medicine, that he believes would work to protect people from the novel coronavirus. The vaccine knocks out a key proofreading enzyme in the SARS viral genome, which cripples the virus and enables it to trigger an immune reaction in mice without causing disease. All coronaviruses, including HCoV EMC/2012, have this proofreading enzyme, Baric says. So, with modifications, the same approach should work for the newly emerging strain.

However, Matthew Frieman, a microbiologist at the University of Maryland School of Medicine in Baltimore, worries that the new virus may not receive significant amounts of researchers’ attention. On 4 December, SARS will become a select agent, as I reported last week. “Everyone who wants to work on SARS is changing their labs over right now,” notes Frieman. With the deadline looming, researchers “may be too busy right now to even think about working on other viruses,” he says.

Frieman also worries that researchers may be discouraged from working on the new virus because of the recent reclassification of SARS. The HCoV EMC/2012 virus is currently not listed as a select agent, but labs must be biosafety level 3 (BSL3) for researchers to work with the virus. Select agent status requires higher security within a BSL3, which Baric hypothesized won’t be required unless the virus proves much more dangerous.

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