The epidemic of Covid-19 infection spreading around the world from China can be contained and controlled, the head of the World Health Organization (WHO) said on Thursday, urging a concerted response by all governments.

“We are calling on every country to act with speed, scale and clear-minded determination,” the WHO’s director general, Tedros Adhanom Ghebreyesus, said at the UN health agency’s Geneva headquarters.

Tedros voiced concern that “some countries have either not taken this seriously enough, or have decided there is nothing they can do,” Reuters reports. “This is not the time to give up. This is not a time for excuses. This is a time for pulling out all the stops,” he added.