The changes to the classification of asymptomatic coronavirus cases emerged on Jan. , in a set of guidance from China’s National Health Commission
. The agency said that it would no longer count patients who had tested positive for the coronavirus but did not display symptoms as “confirmed cases.” Instead, those patients would be counted separately, as “positive diagnosis” patients, and would become confirmed only if they began showing symptoms. Chinese health officials have given little public justification for the labeling change. The National Health Commission did not immediately return a request for comment. Reached by phone, Wu Zunyou, the chief epidemiologist of the Chinese Center for Disease Control and Prevention, directed inquiries to the health commission’s news office. The changes prompted debate among some public health experts. “Adapting definitions during an outbreak is not unusual, with increasing insights and also with prioritizing where efforts need to go,” said Dr. Marion Koopmans, the head of the viroscience department at Erasmus University Medical Center in the Netherlands. By shifting emphasis away from asymptomatic cases, officials can concentrate resources on more serious cases, she said. Dr. Benjamin Cowling, who leads the division of epidemiology and biostatistics at the University of Hong Kong, said the number of cases affected by the change in terminology would most likely be low. He added that attempts to count individual infections become less reliable anyway as outbreaks increase in size. Still, even experts who said that the effect of discounting certain cases would be small said that it would be useful to epidemiologists – and the public – to have a complete count of all cases, including asymptomatic ones.