Roundup: New Omicron subvariants rise in U.S. COVID-19 cases

LOS ANGELES, June 7 (Xinhua) -- Two new Omicron subvariants are on the rise in the United States, adding to concern of health experts whether they may fuel a summer surge in COVID-19 cases.

The subvariants, known as BA.4 and BA.5, were estimated to make up nearly 13 percent of all new U.S. COVID-19 cases in the latest week ending June 4, the U.S. Centers for Disease Control and Prevention (CDC) said on Tuesday.