Just five states have accounted for about 43% of new coronavirus cases over the last week, according to data from Johns Hopkins University.
New York, Michigan, Florida, Pennsylvania and New Jersey had for more than 196,400 of the country's 453,360 cases reported in the last week, according to data available Wednesday morning.
Those states are home to just 22% of the US population, according to estimates from the US Census Bureau.
Case rates have risen especially in Michigan lately, averaging more than 6,600 cases a day over a week now against 1,350 daily cases five weeks ago. And elected officials and health experts have said highly contagious variants such as B.1.1.7 have helped spur increases there and in other parts of the country. Though vaccination rates have increased nationally, not enough people have been inoculated to outpace the spread. And with more-transmissible variants spreading, surges like Michigan's may soon be seen more widely, epidemiologist Dr. Michael Osterholm said.