China sees drop in coronavirus cases after criteria change
BEIJING: China reported yesterday the lowest number of confirmed cases of the coronavirus since late January, due in part to a change in diagnostic criteria for patients in Hubei province, the epicentre of the outbreak.
China had 394 new confirmed cases on Wednesday, the National Health Commission (NHC) said, sharply down from 1,749 cases a day earlier and the lowest since Jan 23.
That brings the total accumulated number of confirmed cases in China to 74,576.
Just how cases are diagnosed and confirmed has had a big impact on official tallies, and changes in the method have raised questions about the extent to which daily tallies accurately reflect the state of the outbreak.
Initially, the authorities were using nucleic acid tests to identify the presence of the virus, but such tests require days of processing, and there were also shortages of nucleic acid.
So last week, Hubei introduced a new, quicker diagnostic method through computerised tomography (CT) scans, which use X-rays, to reveal lung infections and to confirm the presence of the virus.
The CT scan method of diagnosis resulted in suspected cases that showed signs of pneumonia, but did not test positive for genetic traces of the virus, being counted as confirmed cases of Covid-19.
That led to a surge of more than 15,000 new infections for Feb 12, and sparked unfounded fears that the virus was suddenly spreading much faster.
On Wednesday, the NHC said it was reverting to nucleic acid tests, the second change in the methodin just over a week.
"It is not normal for case definitions to be changed so frequently," professor of epidemiology at Hong Kong University Ben Cowling was quoted in Bloomberg as saying.
As a result of the change, Hubei, which accounts for most of China's infections, saw a sharp drop in confirmed cases.
Separately, scientists in China who studied nose and throat swabs from 18 patients say the virus could be more contagious than previously thought.
The preliminary findings published on Wednesday in the New England Journal of Medicine show the virus behaves more like influenza than other closely related viruses and can be passed on by people before they show symptoms. - REUTERS