The chief epidemiologist of the state of Louisiana, Doctor Raoult Ratard, said the virulent vibrio vulnificus, a bacteria that is part of the cholera family, preys mostly on people who already suffer chronic illness.

"I am not surprised that some people have been exposed to it and that it turned into blood poisoning," he told reporters in the Louisiana capital of Baton Rouge.

"But a lot of people have been exposed to sea water, where this bacteria lives, and will not get sick.

"This is not transmitted person to person and its not going to spread," he said, adding however that nursing homes and hospice patients were particularly vulnerable.

While Ratard said people should avoid drinking and wading in the waters that cover large swathes of the city of jazz, he said the best antidote to disease after being exposed was a scrubbing with soap and water.

Tom Skinner, a spokesman for the government's Centers for Disease Control and Prevention (CDC) said one case was reported in an evacuee who landed up in Texas and the others in Mississippi.

Skinner said all the victims had been evacuated from areas pounded last week by Katrina. He added that more deaths were likely.

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