India, Aug. 11 -- A new COVID-19 variant called XFG, nicknamed "Stratus," is spreading quickly in the United States and is now the third most common strain this summer.

Notably, XFG is a mix of two other variants - F.7 and LP.8.1.2, the latter being the second most common in the U.S.

First found in Southeast Asia in January, XFG made up almost none of the cases in the U.S. until May. By late June, it had risen to 14 percent of cases, according to the Centers for Disease Control and Prevention (CDC).

Globally, the World Health Organization (WHO) reported that XFG cases jumped from 7.4 percent in early May to 22.7 percent by the end of the month.

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The WHO...