GENEVA — The number of new coronavirus infections in the last week jumped by about 55%, although the number of deaths remained stable, the World Health Organization said in its latest pandemic report.

In the weekly report issued Tuesday night, the U.N. health agency said there were about 15 million new COVID-19 cases last week and more than 43,000 deaths. Every world region reported a rise in COVID-19 cases except for Africa, where officials saw an 11% drop.

Last week, WHO noted a pandemic record high of 9.5 million new infections in a single week, calling it a “tsunami” of disease.

WHO said the extremely contagious omicron variant continues to define the pandemic globally and is now crowding out the previously dominant delta variant. It said omicron, which was first detected in southern Africa in late November, accounts for nearly 59% of all sequences shared with the largest publicly available global database of viruses. WHO said omicron had now proven to have a shorter doubling time, with increasing evidence it was able to “evade immunity.” It also noted there were numerous studies that it is less severe compared to previous variants.

After a steep rise in omicron cases in South Africa after the variant was first detected, the epidemic quickly dropped and experts believe the wave has now passed. WHO said this week that after a continuous rise of COVID-19 across Africa, cases fell this week for the first time.

Scientists in Britain and the U.S. say there are early signs the crush of omicron may have peaked, but they are still uncertain how the next phase of the pandemic might unfold. WHO noted the Americas reported the highest-ever number of COVID-19 cases this week, with a 78% spike, mainly driven by the U.S.

The number of new cases in Europe rose by 31%, while there was a 10% drop in deaths.

The biggest jump in COVID-19 infections was noted in Southeast Asia, where cases increased by more than 400%, with the largest numbers reported in India, Timor-Leste, Thailand and Bangladesh. The numbers of deaths in the region fell by 6%.

The omicron variant spreads even more easily than other coronavirus strains, and has already become dominant in many countries. It also more easily infects those who have been vaccinated or had previously been infected by prior versions of the virus. However, early studies show omicron is less likely to cause severe illness than the previous delta variant, and vaccination and a booster still offer strong protection from serious illness, hospitalization and death.