BEIJING, March 26 (Xinhua) -- China is still under great pressure in preventing the spread of the novel coronavirus disease (COVID-19) as 23 provincial-level regions have reported imported infection cases, a health official said Thursday.

Long-term prevention and control preparations should be made, said Mi Feng with the National Health Commission at a press conference.

By the end of Wednesday, a total of 541 imported cases have been reported, Mi said.

No new domestically transmitted cases were reported Wednesday, Mi said, noting that a total of 25 provincial-level regions and the Xinjiang Production and Construction Corps are clear of COVID-19 cases.