QINGDAO, Oct. 18 (Xinhua) -- Qingdao has ordered hospitals to strengthen management and monitoring of key departments, including fever clinics, emergency units, and CT rooms, after 13 confirmed COVID-19 cases emerged in the city.

The coastal city in east China's Shandong Province has also asked hospitals to intensify training of medical personnel, and strictly implement infection prevention and control measures for medical personnel, patients, and people accompanying sick persons.

Qingdao has tested all its 11 million residents, with no new positive cases.

Inadequate disinfection in the CT room of the Qingdao Chest Hospital led to the new cluster of COVID-19 infections in the city. The hospital is undergoing thorough disinfection and testing, according to Luan Xin, deputy mayor of the city.

On Saturday, an asymptomatic coronavirus carrier was discharged after treatment. The carrier is one of two stevedores who handled imported frozen seafood at the Qingdao port and were found to have asymptomatic COVID-19 on Sept. 24. One of these two carriers was diagnosed with full COVID-19 on Oct. 14.

Patients discharged from hospital will be transferred to a designated location for a 14-day quarantine, where they will undergo more nucleic acid tests.

Centralized isolation can only end if the test result is negative and the person has no respiratory symptoms, fever or cough, doctors said.