BRUSSELS — The omicron variant kept the world off balance Wednesday as infections from the mutant coronavirus cropped up in more corners of the globe, with one official lamenting that the wait for more scientific information on its dangers feels like “an eternity.”

At the same time the omicron is spreading new fear and uncertainty, the dominant delta variant is still creating havoc, especially in Europe, where many countries are dealing with a surge in infections and hospitalizations and some are considering making vaccinations mandatory.

Much is still unknown about the highly mutated omicron variant, including how contagious it is and whether it can evade vaccines. But governments have rushed to impose travel bans and other restrictions in hopes of containing it.

At least 23 countries, including much of Western Europe but not the U.S., have recorded cases of it, and the number is expected to rise, according to the World Health Organization. Nigeria and Saudi Arabia reported omicron infections Wednesday, marking the first known cases in West Africa and the Persian Gulf region.

Showing an increasingly complicated web of contagion, Japan reported an omicron case in a man who had come from Peru via Qatar.

European Union Commission President Ursula von der Leyen said it will take two to three weeks before it becomes fully clear what omicron can do to the world.

“This is, in normal times, a short period. In pandemic times, it’s an eternity,” she said.

South African researchers alerted the WHO to omicron last week. It is not known where or when the variant first emerged, though it is clear it was circulating in Europe several days before that alert.