The XFG strain, nicknamed “Stratus,” is the predominant variant currently circulating. It has been on the rise since May in the United States and comprised 65% of variants in circulation as of Aug. 9, according to the CDC.

CDC wastewater also shows the XFG variant — nicknamed stratus — is most common in the U.S. Stratus can cause a “razor blade” sore throat and is considered a “variant under monitoring” by the World Health Organization. The WHO said the variant is only marginally better at evading people's immune systems and vaccines still work against it.