Wuhan, the epicentre of the novel coronavirus outbreak in China, reported on Monday its first cluster of infections since a lockdown on the city was lifted a month ago, stoking concerns of a wider resurgence of the disease.
The new infections sounded a note of caution amid efforts to ease coronavirus-related restrictions across China as businesses restart and individuals get back to work.
Wuhan reported five new confirmed cases, all from the same residential compound.
One was the wife of an 89-year-old patient reported a day earlier in the first confirmed case in the central city in more than a month.
“At present, the task of epidemic prevention and control in the city is still very heavy,” the Wuhan health authority said in a statement.
“We must resolutely contain the risk of a rebound.”
All of the latest cases were previously classified as asymptomatic, people who test positive for the virus and are capable of infecting others but do not show clinical signs such as a fever.
The number of asymptomatic cases in China is not known, as they only appear on the radar of health officials when they show up positive during tests conducted as part of contact tracing and health checks.
China does not include asymptomatic cases in its overall tally of confirmed cases, now at 82,918, until they exhibit signs of infection.
Mainland China has reported 4,633 deaths.
Hundreds of asymptomatic cases in Wuhan, which was released on April 8 from a months-long lockdown, are being monitored.
The numbers of new cases reported in China since April have been small compared with the thousands confirmed every day in February, thanks to a nationwide regime of screening, testing and quarantine.
The government said on Friday cinemas, museums and other venues would gradually be reopened, though restrictions including mandatory reservations and a limit on numbers of visitors would be in place.
The financial hub of Shanghai has reopened some night spots and Walt Disney Co reopened its Shanghai Disneyland park on Monday to a reduced number of visitors.
New outbreaks in China in the past two months have mainly developed in residential compounds or at hospitals.
The national health authority called for stronger protocols at laboratories handling samples of coronavirus strains and human nucleic acid tests, and said tests should be carried out under appropriate laboratory settings.
Transport of samples and material that could be infectious must be strictly managed and accounted for, the National Health Commission said.
Mi Feng, spokesman at the National Health Commission, said new infections in seven provinces were being traced.
“In the past 14 days, seven provinces have reported new locally transmitted cases, with cases involving clusters continuing to increase,” Mi told a media briefing, .
“We need to investigate and determine the origin of the infections and transmission routes.”
The northeastern province of Jilin, which on Saturday reported a cluster of infections in one of its cities, Shulan, reported three additional cases.
Shulan has been marked a high-risk area, the only place in China currently with that designation.
“We’re now in a ‘war-time’ mode,” said Jin Hua, the mayor of Shulan, which until the weekend had reported no local cases for more than 70 days.
Shulan has imposed a lockdown on its 600,000 residents since the weekend, with just one member of a household being allowed out each day to buy necessities.
One of the three cases confirmed in Jilin province on May 10 was from Shulan. The other two were uncovered through contact tracing of people who were in contact with earlier Shulan cases.
Nearby Liaoning and Heilongjiang provinces each reported one case, adding to worries about a resurgence of the outbreak in the region.
A 70-year-old patient in Harbin, capital of Heilongjiang, had tested negative seven times before results turned positive.
Of the new cases, seven were so-called imported cases in the northern region of Inner Mongolia involving travellers from abroad.
Across China, the number of new asymptomatic coronavirus cases fell to 12 on May 10 compared with 20 reported a day earlier.