The repatriation of 565 Japanese citizens from Wuhan, China, in late January offered scientists an unexpected opportunity to learn a bit more about the novel coronavirus (2019-nCoV) raging in that city. To avoid domestic spread of the virus, Japanese officials screened every passenger for disease symptoms and tested them for the virus after they landed. Eight tested positive, but four of those had no symptoms at all, says epidemiologist Hiroshi Nishiura of Hokkaido University, Sapporo—which is a bright red flag for epidemiologists who are trying to figure out what the fast-moving epidemic has in store for humanity. If many infections go unnoticed, as the Japanese finding suggests, that vastly complicates efforts to contain the outbreak.
Two months after 2019-nCoV emerged—and with well over 20,000 cases and 427 deaths as of 4 February—mathematical modelers have been racing to predict where the virus will move next, how big a toll it might ultimately take, and whether isolating patients and limiting travel will slow it. But to make confident predictions, they need to know much more about how easily the virus spreads, how sick it makes people, and whether infected people with no symptoms can still infect others.
Some of that information is coming out of China. But amid the all-out battle to control the virus, and with diagnostic capabilities in short supply, Chinese researchers cannot answer all the questions. Countries with just a handful of cases, such as Japan, can also reveal important data, says Preben Aavitsland of the Norwegian Institute of Public Health. “It’s up to all countries now that receive cases to collect as much information as possible.”
With the limited information so far, scientists are sketching out possible paths that the virus might take, weighing the likelihoods of each, and trying to determine the fallout. “We’re at this stage where defined scenarios and the evidence for and against them are really important because it allows people to plan better,” says Marc Lipsitch, an epidemiologist at the Harvard T.H. Chan School of Public Health. These scenarios break into two broad categories: The world gets the virus under control—or it doesn’t.
— Martin Enserink (@martinenserink) February 5, 2020