The international community must step up efforts to stem the coronavirus outbreak amid worrying infection trends in Iran and South Korea, World Health Organisation chief Tedros Adhanom Ghebreyesus says.

"The window of opportunity is still there but our window of opportunity is narrowing," he told a press briefing in Geneva on Friday (local time).

Countries have so far not responded adequately to the WHO's appeal for US$61.5 million (A$92.7 million) to fund its global Covid-19 response plan, Mr Tedros said.

His comments came as authorities in the Chinese province of Hubei revised the number of new cases it reported on February 19 to 775, from 349 previously.

Earlier on Friday, provincial authorities said they would add back some cases to their tally of the disease after they adjusted their methodology to count only cases that were detected with genetic tests rather than with CT scans.

Officials later concluded on Friday that it was a mistake to have removed cases that were already counted.

Its previous tally of 349 cases was the lowest it reported since January 25.

Hubei Party secretary Ying Yong on Friday ordered the cases to be added back to the tally and said that whoever removed them would be held responsible, Tu Yuanchao, a senior official at Hubei's health commission said.

Source: 9News