Asymptomatic coronavirus cases are those who carry the virus but do not show any symptoms and can cause sporadic clusters of infection

For the first time since the COVID-19 outbreak, China on Wednesday revealed the presence of 1,541 asymptomatic cases carrying the deadly novel coronavirus, raising concerns of a second wave of infections amid the relaxation of stringent measures in the country initiated to contain the deadly disease.

Asymptomatic coronavirus cases are those who carry the virus but do not show any symptoms and can cause sporadic clusters of infections.

In a surprise announcement on Tuesday, China's National Health Commission (NHC) said it would begin to release the data of asymptomatic patients.

A total of 1,541 asymptomatic patients infected with COVID-19 have been put under medical observation in China by the end of Monday, including 205 imported cases, state-run Xinhua news agency quoted the NHC in a statement.

Besides the asymptomatic cases, there are reports of 35 new imported cases and one domestic infection, NHC said on Wednesday.

The total number of imported cases has risen to 806, it said.

Seven more people have died of the disease, taking the total number to 3,312.

As of Tuesday, a total of 81,554 confirmed cases of the COVID-19 had been reported on the Chinese mainland.

The announcement about asymptomatic cases came as the other countries are including asymptomatic cases in their number of confirmed cases for their potential to infect others.

Hong Kong-based South China Morning Post reported that the data suggested that by the end of February, more than 43,000 people in mainland China had tested positive for the coronavirus but had no immediate symptoms.

They were not included in the official tally of the confirmed cases.

There is no official explanation why these cases have not been included earlier.

Starting on Wednesday, China will publish the number and conditions of asymptomatic people due to heightened concerns over the risks posed by these stealth virus carriers, who were excluded from the official tally of confirmed cases, Chang Jile, head of NHC's disease control bureau, said on Tuesday.

Both asymptomatic cases and their close contacts will be quarantined in centralised facilities for 14 days. These patients won't be released until they test negative for the virus twice, he added.

'The Commission has always attached great importance to asymptomatic infections and taken strict measures to cope with such cases and their close contacts,' he said.

The decline of coronavirus cases even in its epicentres in Hubei province and its capital Wuhan prompted China to relax its lockdown permitting people to travel out.

China, which has banned new arrivals of foreigners to minimise imported cases, is limping back to normal with most of the factories and businesses humming with activity.

While releasing the figures of the asymptomatic cases, the NHC said a previous study showed that the viral load in samples from asymptomatic infected patients is not much different from that of confirmed cases.

The symptom-free individuals infected with COVID-19 may lead to further spreading of the disease, but the infectivity of asymptomatic cases is still unclear, the NHC statement said.

Some experts believe that without coughing or sneezing, asymptomatic infections may be less infectious, it said.

Unconfirmed reports also said that China plans to do large scale serological testing of its population to detect the presence of antibodies against a microorganism.

A serologic test can determine whether a person has been exposed to a particular microorganism.

As China steps up screening and quarantine of symptom-free patients, health authorities are also rushing to take samples in areas severely affected by the virus for epidemiologic research on asymptomatic cases in a bid to improve its overall disease control measures, Chang said.

'Monitoring data has shown that some asymptomatic people have caused second-generation transmission among their close contacts, and they have set off a small number of clusters of infections,' Chang said.

While the domestic coronavirus epidemic has abated due to aggressive containment measures, public appeals for releasing more information on asymptomatic people and tightening control over them have been running high, China Daily reported.

During a meeting on Monday, the central leading group for epidemic control headed by Premier Li Keqiang also emphasised the monitoring and managing of asymptomatic infections and their close contacts.