Experts said the soaring death rate in New Orleans may be linked to the rampant obesity and other pre-existing health problems in that city. Nearby, St. John the Baptist Parish, a heavily industrialized area along the Mississippi River with a long history of air quality problems, has one of the highest per capita death rates in the country. And while it may not be possible to conclude what role industrial air pollution has played in that statistic, Dr. Hassig said that, more generally, “what we know is that bad air quality is associated with a lot of respiratory conditions.”

Recent coronavirus projections watched closely by state officials and public health experts have shown the possibility of a less severe impact on the South than earlier forecasts, in terms of deaths and the demand on hospitals. But, Dr. Marrazzo said, the fluctuations underscore the level of uncertainty facing doctors.

“It’s just like walking a tightrope every day,” Dr. Marrazzo said in an interview, “because you don’t know what the wind is going to do and if it’s going to knock you over.”

The majority of Southeastern states under conservative control have declined to expand Medicaid insurance for the working poor under the Affordable Care Act, on the argument that the state’s contribution to such expansions, which would insure millions of working-class people, might eventually wreck state budgets.

That has left a number of Southern hospitals in shaky financial health, and has led to widespread closures in states like Tennessee.

Although Louisiana expanded Medicaid in 2016, the impact of the virus there nonetheless appears to be falling disproportionately on people of color, who for decades have been systematically denied access to economic opportunities and thus access to better health care. On Monday, Gov. John Bel Edwards of Louisiana, a Democrat, said that African-Americans accounted for 70 percent of all coronavirus deaths in the state, even though they make up about a third of total residents.