In addition to the U.S., the delta variant has been detected in 103 countries and is predicted to become the dominant variant globally.

"Based on the estimated transmission advantage of the delta variant, it is expected that delta will rapidly outcompete other variants and become the dominant circulating lineage over the coming months," the World Health Organization said Tuesday.

Worldwide, the number of new Covid-19 cases has increased slightly over the past two weeks, after a seven-week decline, according to the WHO. Covid-19-related deaths, however, continued to decline, reaching the lowest point since October 2020.