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The novel coronavirus may have seemed to appear out of nowhere. But epidemiologists, like Columbia University’s Dr. Stephen Morse, have been tracking what he calls “emerging viruses” for decades.
Morse said that he and his colleagues have been on high alert since the SARS outbreak in 2003, which infected more than 8,000 people in 26 countries before being effectively stopped. Epidemiologists went to China to test horseshoe bats, which they believed carried the virus, and found they carry numerous coronaviruses related to SARS.
“So it really wasn't a matter of ‘if’ something like SARS would come back into the human population, it was really a matter of ‘when’ and what it would look like,” Morse said. “SARS should have been a warning to us.”
Morse and his fellow epidemiologists believe the virus that causes COVID-19 probably originated in the same bats as the 2003 strain of SARS. This coronavirus is so similar to SARS, in fact, that scientists are referring to it as SARS Coronavirus 2. Unlike SARS, however, the novel coronavirus spreads much more rapidly and causes less severe symptoms. That means people who aren't even aware they've been exposed can continue to spread it.
Epidemiologists aren’t just tracing the virus back to bats; they’re also tracing who might have been infected, using a technique called “contact tracing.”
“Contact tracing is very much the essential part of what we might call the shoe leather or detective part of epidemiology,” Morse said. “You identify a case, someone you think has the infection or that has a good chance of having the infection. And then you try to identify everyone they have been in contact with.”
That process becomes exponentially more difficult as people board planes, touch shared surfaces, and use public transit. At a certain point, epidemiologists can no longer identify specific sources and refer to cases as being contracted via “community spread.”
“Community spread is very much like what we see with flu or other respiratory infections, it's occurring within some area," Morse said. "It's not clear how someone got it. But very clearly there are a number of people in an area who are in a community who are infected and passing it on to others.”
Many places in the U.S. have entered the community spread phase, where a single person cannot be identified as the source. Still, Morse doesn’t think it’s time for panic — but rather precautions.
“I don't want to underestimate it. But at the same time, you know, it's not going to look like a movie “Contagion” or the apocalypse,” he said. “With public health, we're always struggling with that. That issue of how to balance between complacency or being blasé about it and scaring people because we don't want to do either.“