GENEVA, Feb. 18 (Xinhua) -- The chief of World Health Organization (WHO) said Tuesday that no evidence so far has suggested a sustained local transmission of COVID-19 outside China, except in some specific situations like the Diamond Princess cruise ship.

At a daily COVID briefing, WHO Director-General Tedros Adhanom Ghebreyesus said that his agency does not have enough data at the moment on cases outside China to make a meaningful comparison on the severity of disease or the case fatality rate.

"We're following up with countries to get more information about what happens about each case and the outcome," he said. "However, we have not yet seen the sustained local transmission, except in specific circumstances like the Diamond Princess cruise ship."

The Diamond Princess cruise ship, which was carrying more than 3,700 passengers and crew, has been kept in a two-week quarantine period off the Yokohama Port, Japan, after an 80-year-old passenger on board from Hong Kong was found infected with COVID-19.

So far the total number of confirmed infections from the ship has risen to 542, according to Japanese authorities.