China on Wednesday downgraded the risk level of the coronavirus in its epicentre Wuhan from high to medium and resumed bus services within the city for the first time since the nine-week lockdown even as a new study said thousands of positive cases there may have gone under the radar.
China has decided to lift the three-month lockdown on more than 56 million people in the central Hubei province.
However, the prolonged lockdown of Hubei's capital Wuhan will end on April 8, lifting the mass quarantine over the city with a population of over 11 million.
Also, Wuhan will resume commercial flights from April 8, excluding international flights and flights to and from Beijing.
The government has downgraded the risk level of Wuhan for COVID-19 outbreak from high to medium, state-run China Daily reported on Wednesday.
While Hubei and Wuhan has not reported any new COVID-19 case, four people died in the city taking the death toll in China to 3,281, the National Health Commission (NHC) said on Wednesday.
China on Wednesday said that no new domestically transmitted case was reported on the Chinese mainland on Tuesday but 47 new imported cases were reported in the country, taking the total number of such cases to 474, it said.
The Chinese Foreign Ministry said on Tuesday that majority of the imported cases are the Chinese nationals returning from abroad.
Of the 427 confirmed imported cases reported on March 23, 380 are Chinese and the rest 47 are foreign nationals, it said.
Also on Tuesday, four deaths and 33 new suspected cases were reported on the mainland with three of the deaths reported in Hubei.
The overall confirmed cases on the mainland reached 81,218 by the end of Tuesday. This included 3,281 people who died of the disease, 4,287 patients still being treated and 73,650 patients discharged after recovery, the NHC said.
While China began to relax measures taken to control the coronavirus, a Chinese health official said China must not loosen-up epidemic control as the flow of people increasing.
China should stick to strict measures on epidemic prevention and control as the country resumes work and production and the flow of people increases, Mi Feng an official with the NHC told media here.
"We must take strict measures to prevent imported COVID-19 cases from abroad and a rebound of the epidemic domestically," Mi stressed.
China is resuming normal operation of road traffic in Hubei province, the country's hardest-hit region by the novel coronavirus, to facilitate the province in returning to normal economic activity, an official notice said.
Meanwhile, over 800 people stuck in Hubei province since January 23 lockdown have arrived in Beijing, official media reported.
As the virus abated in Wuhan and Hubei province, over 21,000 medical personnel who were deployed there to control the virus outbreak left the province on Tuesday.
There are still 16,558 medical workers belonging to 139 medical teams who are fighting the virus in Wuhan. China had deployed over 42000 medical personnel including the staff drawn from the military.
As the restrictions in Wuhan relaxed, a new study said roughly 60 per cent of people who contracted the coronavirus in Wuhan were asymptomatic or very mild cases not reported to the authorities.
The estimate was based on about 26,000 laboratory-confirmed cases recorded in the city between December and February, according to a study led by a group of Chinese doctors published in the medRxiv preprint platform early this month.
The paper has not been peer-reviewed, Hong Kong based South China Morning Post reported.
The researchers used lab tests as the basis of their assessment rather than Chinese government data on confirmed cases because the authorities used symptomatic manifestations and abnormal lung scans to classify patients.
The lab test data allowed the doctors from Tongji Medical College in Wuhan, Fudan University and Harvard University, to create models regardless of whether the patients had symptoms, the Post report said.
The study said that based on their models, the total number of infections citywide on February 18 could have exceeded 125,000.
We predicted the cumulative number of ascertained cases to be 26,252 by February 18, close to the actual reported number of 25,961, while the estimated cumulative number of total cases was 125,959, it said.
Wuhan reported 38,020 confirmed cases on February 18.
The study also estimated that 36,798 people had been infected overall as of January 25.