A coronavirus alarm bell is going off in the Midwest

A cluster of states in the Midwest are seeing more of their coronavirus tests coming back positive — potentially an early indicator of a growing outbreak.

The state of play: A high positive rate means that a higher share of those getting tested are sick. That could be because there are more sick people, or because a state isn't doing enough testing.

The big picture: Even though positivity rates are holding steady in some hotspots, that's not good news when they're plateauing at high levels.

• Florida, Nevada, Mississippi and Alabama are all still hovering near a 20% positivity rate, and the positivity rate is still rising in Texas.
• That means that those states have a high number of cases, aren't doing enough testing or, most likely, some combination of the two.
• Arizona's rate is decreasing, although it's still around 15%.

Between the lines: Total U.S. testing this week decreased by nearly 13% compared to the week before, muddying the picture of what's going on in some states.

• Arkansas, for example, saw an increase in its positivity rate over the last two weeks, as its testing decreased by 34%.
• Nebraska, on the other hand, is also facing a growing positivity rate, but its testing increased by 9% — a bad combo.

The good news: New York has transformed itself from a national nightmare into a model for every other state, with a positivity rate of 1%. That suggests that it is testing more than enough people, and very few of them are sick.