https://www.wsj.com/articles/sharp-rise-in-coronavirus-cases-raises-questions-about-outbreaks-peak-11581617783
New cases of the coronavirus rose sharply after Chinese authorities changed the criteria for diagnosing the illness, raising questions about how soon the outbreak will peak.
On Thursday, health officials in Hubei province, the epicenter of the infections, announced the largest one-day jump in cases—14,840 on Wednesday, about nine times the number of new cases a day earlier. Epidemiologists, government officials and investors might now need to recalibrate their projections for the trajectory of a virus that remains little understood.
In recent days, investors had pushed U.S. stocks to records as Chinese officials touted gains in the fight against the fast-spreading illness that has gripped central China for the past month, fixing their attention on one number—a drop in the growth rate of new infections—that suggested the virus was running out of steam.
Such a dramatic surge in cases as announced Thursday is likely a one-off. It reflects the shift in how Hubei province authorities are classifying patients as having clinically confirmed infections after they are diagnosed by a doctor, such as through an X-ray, rather than just counting those patients who have positive laboratory identification of the virus.
The new practice isn’t a standard way to diagnose the presence of a specific virus.
“This does not represent a significant change in trajectory of the outbreak,” said Michael Ryan, executive director of the World Health Organization’s Health Emergencies Program. He called the jump in cases “an after-fact of reporting.”
Dr. Ryan said the move would allow authorities to do more public-health investigations, such as by tracking down patients’ contacts, which are needed to contain the outbreak.