A ray of hope in the coronavirus curve

HEADLINES ABOUT the new coronavirus that started in China are grim. More than 1,000 people have died, exceeding the toll from the SARS outbreak in 2003. Despite stringent controls on movement, there are 64,000 confirmed or suspected cases of infections in China. And it is spreading around the world. But there is some good news: the number of new cases reported daily in China has been on a downward trend since February 4th. That is to say, transmissions are still occurring but at a slower rate, an indication that public-health authorities are making progress in their battle against the bug.

Trying to forecast the trajectory of a new virus is complex, with scant initial information about how infectious it is. Several scientists made valiant attempts based on early data from China. Some warned that it might not peak until May, but that was before China implemented strict containment measures. The more pessimistic ones now look too gloomy. Cheng-Chih Hsu, a chemist at National Taiwan University, plugged different scenarios into a simple model for estimating the spread of epidemics (the incidence of daily infections typically resemble bell curves, with slightly fatter tails as transmissions peter out). The tally of confirmed cases so far closely fits a seemingly optimistic forecast by Zhong Nanshan, a Chinese respiratory expert, who said on January 28th that transmissions would peak within two weeks.