Mainland China has reported the lowest number of confirmed cases of a new coronavirus since late January, partly because of 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 1749 cases a day earlier and the lowest since January 23.
That brings the total accumulated number of confirmed cases in mainland China to 74,576.
The new coronavirus emerged in the city of Wuhan, the capital of the central province of Hubei, in December, apparently jumping to people in a market selling wildlife.
Just how cases are diagnosed and confirmed has had a big impact on official tallies of cases, and changes in the method have raised questions about the extent to which daily tallies accurately reflect the state of the outbreak.
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Initially, authorities were using nucleic acid tests to identify the presence of the virus, but such tests require days of processing.
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 new method of diagnosis meant that suspected cases of the coronavirus who showed signs of pneumonia in the CT scan chest X-rays, but did not test positive for genetic traces of the virus, were counted as confirmed cases.
That led to a surge of more than 15,000 new coronavirus infections for February 12, and sparked unfounded fears that the virus was suddenly spreading much faster.
But on Wednesday, the NHC said it was removing that category of clinically diagnosed cases from its criteria for confirmed cases, meaning 279 cases would be removed from the Hubei tally.
The commission said the nucleic acid test was the preferred method of diagnosis.
Allen Cheng, an infectious diseases expert at Monash University in Melbourne, said he did not understand why cases diagnosed by different methods at different times had to be added or subtracted to tallies on other days.
"Best practice would be to assign the cases to the date they are reported. This was also an issue with the large number of cases reported on February 12," he said.
Excluding Hubei, the number of new confirmed cases in mainland China stood at 45 on Wednesday, down from 56 a day earlier and falling for the 16th consecutive day.
The situation is still severe, although efforts to curb the coronavirus in Hubei have made progress, Vice Premier Sun Chunlan said on Wednesday.
