But he said: "The stabilization in cases in the last number of days is very reassuring and it is to a great extent the result of the huge public health operation in China".
Efforts are gaining pace after China shared the virus' genetic code.
The new classification system of COVID-19 was meant to ensure that "patients can receive standardized treatment according to confirmed cases as early as possible to further improve the success rate of treatment", according to the Hubei Province Health Commission.
The country's National Health Commission said 2,015 new cases were counted on Tuesday, the second straight daily decline and down from almost 3,900 a week ago.
Dr Tedros also praised Cambodia for taking in the Westerdam, a United States cruise ship that had earlier been turned away from ports in Japan, Thailand and Taiwan despite having no sick patients on board. The death toll and number of cases only began to soar afterwards, going from one fatality on January 11 to more than 630 barely four weeks later.
Jiang Chaoliang, Hubei's party secretary, will be replaced by Shanghai mayor Ying Yong, while Wuhan party chief Ma Guoqiang will be replaced by an official from Shandong, Xinhua news agency reported.
The biggest cluster of cases outside China is on a cruise ship quarantined off Japan's coast. Japanese officials on Wednesday said another 39 people had tested positive for the coronavirus, bringing the total to 175.
Temporary coronavirus hospital in converted Wuhan Sports Center
The online newspaper VN Express cited a senior official of Vinh Phuc province as reporting an increase in cases in Son Loi commune. "In Singapore, we are at the beginning".
The new name is taken from the words "corona", "virus" and "disease", with 2019 representing the year that it emerged (the outbreak was reported to the World Health Organization on 31 December).
The incidents occurred amid the outbreak of the virus in China that has already infected more than 40,000 people all over the world.
GSMA said Wednesday that this year's edition of Mobile World Congress will no longer be held as planned in Barcelona, Spain, on February 24-27.
Many countries have imposed travel restrictions for travelers coming from China to avoid the spread of the virus. A gauge of global equities hit a record high yesterday. The number of deaths has overtaken that of the Sars epidemic in 2002-2003.
The economy has also been upended, with factory closures hitting supply chains from auto makers to tech firms. "It is important that these also be counted", she told Reuters.
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