Disease is one of the greatest threats now facing those trying to recover from Katrina:

Flooding in New Orleans could cause major public-health problems ranging from diarrhea to West Nile virus, experts said. But on Tuesday, beleaguered medical workers were struggling to keep patients alive.

Contaminated floodwaters can spread such bacteria as E. coli and salmonella, which can be fatal for the very young, the very old and others with weak immune systems, said Dr. Delia Rivera, an expert in infectious diseases at the University of Miami School of Medicine.

Experts said it could be several weeks before the floodwaters -- polluted with toxic contaminants including human feces, gasoline and chemicals from industrial sites -- are pumped from the city.

The foul water could cause skin rashes and other ailments, Rivera said.

But while flooding can potentially spread such epidemic-causing diseases as typhoid fever, cholera and leptospirosis, they are not likely to be a problem in the short term, she said, because they are not endemic in the United States.

A more serious medium-term risk, Rivera said, might be mosquito-borne diseases such as malaria, dengue fever and West Nile virus.

``In an area like New Orleans, it could happen,'' she said.

Federal and state officials already have launched a mosquito-control program for the region, said Christina Pearson of the Department of Health and Human Services.