How much will the coronavirus spread, and what precautions should you take?

Science & Health

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Photo credit: SupChina illustration by Derek Zheng

The number of people infected with the Wuhan coronavirus has now surpassed 6,000, according to reports by Chinese state media. Though it is widely agreed that it is not as deadly a virus as SARS, the extent that it will continue to spread is a matter of some disagreement.

In China, three health experts have now stated they believe the epidemic will reach its peak before mid-February.

  • Zhōng Nánshān 钟南山, a respiratory expert who played a key role in containing the SARS outbreak, said on January 28 that this outbreak will reach its peak in “one week or about 10 days.”
  • Gāo Fú 高福, the director of the Chinese Center for Disease Control and Prevention, has said (in Chinese) that the Lantern Festival (February 8) will see “a turn for the better” in the crisis.
  • Zéng Guāng 曾光, the chief epidemiologist of the Chinese CDC, also said that February 8 may see a turnaround.

Outside of mainland China, researchers aren’t so sure. According to researchers in the U.S. and Canada cited by the AFP, the virus “will afflict a minimum of tens of thousands of people and will last at least several months.”

The spread depends partly, but not entirely, on an “R0,” or reproduction number, pronounced R-naught. Ed Yong explains in The Atlantic:

In brief, R0 is the average number of people who will catch the disease from a single infected person, in a population that’s never seen the disease before. If R0 is 3, then on average every case will create three new cases. But even though it seems incredibly straightforward, it’s hard to calculate and tricky to interpret…

In the past week, at least six teams of researchers, along with the World Health Organization, have published estimates of R0 for the new coronavirus. All these groups used different methods, but their results have been mostly consistent, with estimates hovering between 2 and 3.

Between 2 and 3 is higher than the seasonal flu — 1.3 — but lower than SARS — 2 to 5 — and much lower than highly infectious diseases like measles, which can be 12 or higher.

The efficacy of containment measures is another major factor that will determine the spread of the virus, and as Joan Kaufman writes in the Washington Post, China’s politics makes it easier — and harder — to control disease outbreaks:

The immediate challenge of controlling the spread of the virus during the Lunar New Year holiday prompted a travel ban in Wuhan and other nearby cities. Chinese authorities also canceled crowded public events. This isn’t a popular move — but it is in line with global recommendations on social distancing, which stops short of quarantine but reduces person-to-person contact and exposure.

But authorities imposed the ban after 5 million people had left Wuhan, so its effect will be less than intended, given the two-week incubation period. Therefore, the outbreak will probably continue spreading for a while…

China’s health authorities appear to be taking the right steps, but there are cracks in other parts of the response. Media controls, which have tightened under President Xi Jinping, initially impeded the flow of information to the public.

For more definitions of important terms related to the coronavirus, see NPR: Defining the words used in coverage of the Wuhan coronavirus outbreak.

Should you wear a mask in China?

Though a guide from the National Health Commission of the People’s Republic of China states that “wearing a mask is one of the most effective ways to protect you from getting infected,” Zeng Guang, the chief epidemiologist of the Chinese CDC, was quoted in the Global Times as saying there is no need to “wear surgical masks on the streets in Beijing.”

The American CDC and World Health Organization similarly do not list wearing masks as among their top recommendations to stay safe from the coronavirus. Two veteran health and science reporters, Laurie Garrett and Elisabeth Rosenthal, have written in Foreign Policy and the New York Times that washing your hands, wearing gloves, and maintaining your distance from others in public are more important precautions than wearing a mask. Rosenthal explains why a surgical mask was not an everyday necessity for her when she reported on the SARS crisis:

Having a mask with you as a precaution makes sense if you are in the midst of an outbreak, as I was when out reporting in the field during those months. But wearing it constantly is another matter. I donned a mask when visiting hospitals where SARS patients had been housed. I wore it in the markets where wild animals that were the suspected source of the outbreak were being butchered, blood droplets flying. I wore it in crowded enclosed spaces that I couldn’t avoid, like airplanes and trains, as I traveled to cities involved in the outbreak, like Guangzhou and Hong Kong…

But outdoors, infections don’t spread well through the air. Those photos of people walking down streets in China wearing masks are dramatic but uninformed. And remember if a mask has, perchance, intercepted viruses that would have otherwise ended up in your body, then the mask is contaminated. So, in theory, to be protected maybe you should use a new one for each outing.

More updates on the Wuhan coronavirus:

—Lucas Niewenhuis