Straining to handle record numbers of COVID-19 patients, hundreds of the nation’s intensive care units are running out of space and supplies and competing to hire temporary traveling nurses at soaring rates.

Many of the facilities are clustered in the South and West.

An Associated Press analysis of federal hospital data shows that since November, the share of U.S. hospitals nearing the breaking point has doubled. More than 40% of Americans now live in areas running out of ICU space, with only 15% of beds still available.

Intensive care units are the final defense for the sickest of the sick, patients who are nearly suffocating or facing organ failure. Nurses who work in the most stressed ICUs, changing IV bags and monitoring patients on breathing machines, are exhausted.

“You can’t push great people forever. Right? I mean, it just isn’t possible,” said Houston Methodist CEO Dr. Marc Boom, who is among many hospital leaders hoping that the numbers of critically ill COVID-19 patients have begun to plateau.

Worryingly, there’s an average of 20,000 new cases a day in Texas, which has the third-highest death count in the country and more than 13,000 people hospitalized with COVID-19-related symptoms.