The World Health Organization said on  Wednesday  that the coronavirus that causes COVID-19 has infected more than 121,000 people around the world and is present in more than 100 countries has become a pandemic.

Until now, the W.H.O. had avoided using the term to describe the epidemic leapfrogging across the world, for fear of giving the impression that it was unstoppable and countries would give up on trying to contain it. The organization had said earlier in the outbreak that it no longer officially declared when an epidemic reaches pandemic proportions, preferring instead to declare global public health emergencies.

“Pandemic is not a word to use lightly or carelessly,” Dr. Tedros Adhanom Ghebreyesus, chief of the W.H.O., said at a news conference in Geneva.

“We cannot say this loudly enough or clearly enough or often enough,” he added. “All countries can still change the course of this pandemic.”