Where will it be worst?

摘要

AS THE NUMBER of deaths among people infected by the new coronavirus mounts, it is tempting to divide that figure by the number of reported cases and conclude that the result is the fatality rate. Apply such maths to the world's total of confirmed cases and deaths on March 11th and you get a fatality rate of 3.6%. But this figure, which epidemiologists call the "naive" case fatality rate, may be wrong in two different ways. First, many of the infections detected at this early stage of the epidemic are recent, so some will eventually result in deaths. That will push the fatality rate up. Second, many infections have not been spotted because testing for the virus has been patchy. Lots of mild cases of the disease have gone unnoticed. If all infections were actually counted, the result would be a bigger denominator. That would push the fatality rate down. As China began to trace infections more carefully, its fatality rate fell (see chart 1).