Worker Wang Fu wearing a face mask sprays disinfectant at an apartment of a residential compound, as the country is hit by an outbreak of the novel coronavirus, in Beijing, China February 21, 2020. REUTERS/Tingshu Wang

BEIJING (Reuters) - A coronavirus patient initially discharged after recovering in southwestern Sichuan province’s Chengdu city has been readmitted after testing positive during a quarantine period at home, the city’s public health clinical center said on Friday.

The patient tested positive during a check-up 10 days after being discharged, the center said in a statement. Similar cases have been reported in other regions.

The positive result after discharge was likely due to a discrepancy in samples, the state media People’s Daily reported late Friday, citing an expert.

Official guidelines say patients must test negative for the virus twice, with at least a day between tests, before being discharged.

Hospitals had used nose and throat swabs for such tests before discharging patients, but are now required to use samples from lungs, where the virus is most likely to be detected as it develops, Lei Xuezhong, a doctor working on a treatment for coronavirus-caused pneumonia in Sichuan province told People’s Daily.

China’s National Health Commission recommends recovered patients monitor their health for 14 days, wear masks and reduce outdoor activities after leaving hospitals due to risks of contracting other pathogens.