The head of the World Health Organization says COVID-19 is 10 times deadlier than the flu pandemic of 2009 reports NHK.

WHO Director-General Tedros Adhanom Ghebreyesus told reporters in Geneva on Monday that the spread of COVID-19 "accelerates very fast, it decelerates much more slowly."

He said the control measures that countries have implemented to fight the virus "must be lifted slowly, and with control". He added that they cannot be lifted "all at once."

According to NHK, the WHO lists six criteria for countries to use when they consider lifting their restrictions.

The criteria include whether the transmission of coronavirus is controlled, and whether measures are in place to detect, test, isolate and treat every case and trace ever contact.

The Director-General's regular briefing came after President Donald Trump suggested the US will review its funding for the WHO.

Tedros said the US is the largest contributor to his organization. He said he knows that Trump is supportive and that he hopes the US will continue offering funding to the WHO.