BEIJING - A health official said Wednesday China has effectively contained the rapid expansion of COVID-19 cases in Urumqi, capital of Northwest China's Xinjiang Uygur autonomous region, and Dalian of Liaoning province in the northeast.

Experts have been working to isolate the virus and confirm its genome sequence, said Jiao Yahui, an official with the National Health Commission, at a press conference.

Since late July, cluster infections have been reported in Urumqi and Dalian. From July 16 to Aug 4, a total of 670 confirmed cases had been reported in Xinjiang and 90 in Liaoning Province, said Jiao.

The new round of COVID-19 epidemic in the two places has several things in common, including rapid rise in the initial stages, Jiao said.

Besides, the average age of confirmed patients in Xinjiang was only 35 and that in Dalian 41. Most patients showed mild or normal symptoms, Jiao added.

The two places conducted epidemiological investigations rapidly and improved their nucleic acid testing capabilities, Jiao said.