GENEVA, March 4 (Xinhua) -- The epidemic of COVID-19 is becoming increasingly complex, said the chief of World Health Organization (WHO) here on Wednesday, calling for early and aggressive measures to break the chains of transmission and contain its spread.

Noting linked COVID-19 epidemics in several countries, WHO Director-General Tedros Adhanom Ghebreyesus said at a briefing that different countries are in different scenarios, thus "there is no one-size fits all approach".

Against first case, first cluster and first evidence of community transmission, WHO is advising countries on actions, Tredos said, stressing actions now will determine the course of the disease outbreak.

He pointed out the basic actions in each scenario are the same, while the emphasis changes depending on which transmission scenario emerges in a country.

Political commitment is needed in every country, Tedros said, calling for mobilizing the whole of government before cases even arrive and keeping aggressive when cases arrive.

Based on the report of the WHO-China Joint Mission, the WHO chief reminded all countries should educate their populations, expand surveillance, find, isolate and care for every case, trace every contact, and take an all-of-government and all-of-society approach.

"The nature of this virus means we have an opportunity to break the chains of transmission and contain its spread," Tedros said.