GENEVA (AP) — The head of the World Health Organization has warned that “the worst is yet ahead of us” in the coronavirus outbreak, raising new alarm bells about the pandemic just as many countries are beginning to ease restrictive measures.

WHO Director-General Tedros Adhanom Ghebreyesus didn’t specify exactly why he believes that the outbreak that has infected nearly 2.5 million people and killed over 166,000, according to figures compiled by Johns Hopkins University, could get worse. Some people, though, have pointed to the likely future spread of the illness through Africa, where health systems are far less developed.

Tedros alluded to the so-called Spanish flu in 1918 as a reference for the coronavirus outbreak.

“It has a very dangerous combination and this is happening … like the 1918 flu that killed up to 100 million people,” he told reporters in Geneva.

“But now we have technology, we can prevent that disaster, we can prevent that kind of crisis.”

“Trust us. The worst is yet ahead of us,” he said. “Let’s prevent this tragedy. It’s a virus that many people still don’t understand.”