Intensive care units in Montgomery, Ala., are overflowing with Covid-19 patients, pushing them into emergency departments that are not primed to care for them. And Alabama’s capital city could be a harbinger for other parts of the country.

ICU beds are also starting to fill up in places like Minnesota’s Twin Cities; Omaha, Neb.; and the entire state of Rhode Island, according to local health officials and epidemiologists tracking such data, a warning sign of possible health care problems down the road. The availability of ICU beds is one measure of a hospital’s ability to care for its most vulnerable patients — people with severe illness who require more staff to treat them and may need life-support equipment such as a ventilator to breathe. And it’s served as a metric for whether the local health care system is able to handle a coronavirus outbreak, albeit a constantly shifting one.

Some state leaders deny there are problems, saying they are prepared to convert regular hospital beds to ICU beds, if necessary. In the meantime, they are pressing ahead with reopening plans.