In just eight weeks, the Omicron subvariant known as BA.5 has gone from a blip in United States case counts to the dominant version of the coronavirus in the country, now making up more than three-quarters of new cases. Perhaps the most transmissible subvariant yet, BA.5 is driving increases in positive tests, hospitalizations and intensive care admissions across the country.
As of Wednesday, an average of roughly 127,700 known coronavirus cases and 426 deaths were being reported each day in the United States, according to a New York Times database, a marked increase from early July.
Known infections are rising in at least 40 states, particularly in the Great Plains, West and South. Hospitalizations have increased by 19 percent over the past two weeks, and more than 41,800 people are now in American hospitals with the coronavirus on an average day.
The popularity of home testing means that figures for reported cases are now even more of an undercount of the true infection rate than they were in the pandemic’s earlier waves. The share of all tests that come back positive is also rising faster. Federal data show that the risk of catching the virus is increasing in much of the country.
The C.D.C.’s assessment last week of community risk levels, using a hospitalization-based metric, puts about 35 percent of United States counties in the “high risk” category, but those counties are home to about 55 percent of the American population.
In such high-risk areas, the agency recommends wearing masks in public indoor settings. But there are no state-level mask mandates now in force.
President Biden’s coronavirus response team warned Americans last week that they must do more to protect themselves against Covid-19.
“Variants will continue to emerge if the virus circulates globally and in this country,” Dr. Anthony S. Fauci, Mr. Biden’s chief medical adviser for the pandemic, said at a White House news briefing. “We should not let it disrupt our lives. But we cannot deny that it is a reality that we need to deal with.”