Hospitals in at least 25 states are critically short of nurses, doctors, and other staff as coronavirus cases surge across the US, according to the industry’s trade association and a tally conducted by STAT. The situation has gotten so bad that in some places, severely ill patients have been transferred hundreds of miles for an available bed — from Texas to Arizona, and from central Missouri to Iowa. Many of these hospitals spent months building up stockpiles of medical equipment and protective gear in response to Covid-19, but the supplies are of little use without adequate staffing.