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how the coronavirus spreads, who's at risk, and what r0 means
we asked an infectious diseases epidemiologist everything you wanted to know about 2019-ncov
jan 31 2020
4 minute read
marcos silva/getty images
with information (and misinformation) about the novel coronavirus, or 2019-ncov as it’s called, spreading and evolving every hour, we decided to ask an epidemiologist to separate fact from fiction. this new coronavirus belongs to a large family of viruses called coronaviruses, which commonly affect mammals, including camels, cattle, cats, and bats.
here, dr. tara smith, an infectious diseases epidemiologist who primarily researches zoonotic infections (infections transferred between animals and humans), explains what we actually know, what we don’t, and what r0 means exactly.
is the coronavirus zoonotic?
it requires further investigation and it’s still being worked out, but it does seem to be zoonotic. they have the entire genome of the viruses from many people. it seems to be most closely related to the bat coronavirus.
we’re not sure yet if that means it moves directly from bats to people or in the case of sars—it was from bat to an intermediate animal, the civet cat. this is one of the things that a lot of people in china are working on day-to-day and epidemiologists are trying to figure out what the source is.
what do we know about how it spreads between humans?
transmission seems to be like an ordinary respiratory virus, it grows in your upper respiratory tract: in your nose, in your throat, and it is expels typically during coughing. one of the unknowns that we’re still trying to pin down is if it can be transmitted even in the absence of symptoms. with sars and mers, both viruses seemed to transmit only when people were actively symptomatic, so only when they were feeling ill and coughing and sneezing.
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some people will say that this could be transmitted before people get sick — which is more concerning from the standpoint of trying to keep it under control. but again, that’s something we don’t know for sure because we don’t have enough data to say if it can or cannot transmit before symptoms.
what is the r0?
people have given a lot of estimates of the r0 (pronounced “r naught). early estimates say, on average, one person can transmit to one other person or to three other people. some people have been using the higher estimates of that, which causes people to panic.
but that number alone is changing. it doesn’t really tell us much about the virus. viruses can be very transmittable but very mild. think of cold viruses. everyone gets those every year, but very few people get seriously ill from them. i’m seeing a lot of concern about this just because of the potential transmission without knowing very much about the fatality rates.
we know at least 170 deaths attributed to this virus. but we have more than 8,000 cases identified so far. we just don’t know very much about the fatality rate yet. t here’s so many unknowns and so many people are putting out that information suggesting this is the apocalypse. i wish we had all that data so we could alleviate some of these fears. but right now we’re in that grey area in the midst of this epidemic. we don’t know how it’s going to go. we don’t know how it’s going to end. so all we can do is try to let people know about our updates and our current findings and let them know when it gets concerning to us.
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who is most at risk?
those in wuhan. sitting here in north america, i’m not concerned for myself and my family yet. who i’d be most worried about here are the health care workers, making sure that their employers have a plan in place to protect them. if a potential patient comes in and they know what to do with them, they know to mask them, put them in isolation. that was a group that was affected during sars and mers.
what about the general public?
if you have people who are in groups that are usually at risk for respiratory infections, the young, the elderly, the immunocompromised. take normal precautions that you would do anyway during flu season. wash your hands frequently, cover your mouth when you cough, do all of those normal things.
the flu is deadlier than the coronavirus. so why are more people panicked about this?
that’s the thing of being new. new is scary because you don’t know if you get infected, if you would survive it or if your family would survive it. most of us have had the flu at some point in our lives or have family members who have, so it it seems familiar, even though it kills thousands of people every year (the cdc estimates 15 million people were infected, 140,000 were hospitalized and 8,200 people have died from the flu this season). that’s huge but to people, it’s not as scary as this new virus. you know, many people avoid the flu vaccine. it’s the fear of the unknown that i think drives the scare factor. racism has to do with it, too, it’s seen as ‘exotic’ and the ‘other.’
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what other common misconceptions are you seeing?
many. there’s just so much we don’t know yet. the cases are increasing rapidly, part of that may be because more people are getting sick. but part of that is because we’re searching for cases. of course, when you’re actively searching, you’re going to find more. we don’t really know if transmission is really increasing or if it’s just where we’re finding these cases because we’re looking for them.
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