Via STAT, Helen Branswell writes what a lot of people are thinking: Confusion over coronavirus case count in China muddies picture of spread. This is a long excerpt, but you'd better read the whole article:
Infectious diseases experts are losing confidence in the accuracy of China’s count of cases of the novel coronavirus, pointing toward health officials’ shifting definition of cases over time.
Confusion over how China is counting cases of infections is making it harder to know how coronavirus is spreading, even as China is officially reporting that the numbers of new cases reported in recent days have fallen sharply. Many suspect the decline may be attributed in part to shifting case definitions. Earlier this month, China broadened the criteria for newly diagnosed cases in Hubei province, the epicenter of the outbreak, then reversed itself.
“Every time you change the case definition, that then means you have a reset in terms of what you’re actually looking at,” said Michael Osterholm, director of the University of Minnesota’s Center for Infectious Diseases Research and Policy. “I think between the inability to determine the actual number of people infected and how cases are now being called a case means at best you can get trend data, possibly, but not more than that.”
China reported 74,675 cases and 2,121 deaths to the World Health Organization as of Thursday morning, the agency’s director general, Tedros Adhanom Ghebreyesus, said during a daily briefing for reporters. Another 1,076 cases have been reported from 26 other countries, including seven deaths.
From a few dozen cases in early January, China’s daily increase in cases exploded later in the month. The rapid increase of cases in the lead-up to the Lunar New Year led Chinese authorities to impose a quarantine of the entire city of Wuhan, where the outbreak appears to have started, on Jan. 22.
In the days that followed, the quarantine extended to other cities in Hubei province, leaving tens of millions of people under the largest “social distancing” effort of modern times. And still the country’s case count for Covid-19, the disease caused by the coronavirus, rose by between 2,500 and 3,400 cases a day.
On Feb. 12, the national health committee announced that it was changing the way cases were counted in Hubei province. People with symptoms of the disease and with evidence of pneumonia on a CT scan but who had not been tested for presence of the virus — in other words, people who had a clinical diagnosis — would be added to the list of cases.
That day, the country reported a massive increase in cases — over 15,000. But since then, the daily numbers have tumbled. On Wednesday, China announced it was reverting to reporting laboratory-confirmed cases only. When the National Health Committee issued its update for Wednesday, it reported a net increase of only 394 cases — the first time in weeks the daily case increase was under 1,000 cases.
It is not unusual for the case definition to change during an infectious diseases outbreak caused by a new virus. In fact, they have to change as more information becomes apparent. For too long in this outbreak, for example, China only counted people with pneumonia as cases — a fact that blocked their ability to detect people with mild infections. But the relatively rapid about-face on the inclusion of clinically diagnosed cases has amped up the uncertainty about the published numbers.
