Coronavirus cases are on the rise again across more than half of the U.S.

New cases are up by at least 5%, based on a seven-day average, in 26 states as of Sunday, compared with just 12 states a week ago, according to a CNBC analysis of data compiled by Johns Hopkins University. In Arizona, Florida, California and Texas, new cases are declining by at least as much, though those states still accounted for nearly 10,000 new cases combined on Sunday — or about a fourth of all new U.S. cases.

Across the nation, average new cases have climbed three out of the last five days.

Many of the recently growing outbreaks across the country are occurring in the Midwest, including Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, Ohio and the Dakotas. Those states collectively reported more than 7,400 new cases Sunday, according to data collected by Hopkins.

Iowa has reported an average of more than 1,100 new cases a day over the past seven days, more than double from a week ago, according to Hopkins data. Some of that rise, though, is likely because the state began including antigen test results last week. South Dakota has reported an average of more than 290 cases per day over the past week, up over 104% compared with a week ago.

New cases are also still rising in a number of more populous Southern states. Alabama has reported an average of more than 1,400 new cases a day over the past week, up more than 53% from a week ago, according to Hopkins data, and South Carolina has reported an average of over 905 daily infections, up 15% compared with last week.

The steady rise of new cases in these states and others are turning up in the national numbers. New cases nationwide have been on the decline for more than a month, but the rate of decline has slowed over the past few days. Average new cases have hovered between 41,000 and 43,000 over the past week, a level far higher than federal health officials say is acceptable heading into the fall. ...