Hurricane Katrina: Outbreaks of deadly diseases pose a new danger to residents of areas devastated by Hurricane Katrina.
In New Orleans, bodies have been reported floating in the flood water that has submerged large parts of the city.
The sewers have overflowed, and for days thousands of survivors have been living in squalid conditions with no sanitation or clean water.
Experts say these conditions provide an ideal breeding ground for diseases such as cholera, typhoid and West Nile virus, and warn that swift action needs to be taken to prevent an outbreak.
Matthias Schmale, international director of the British Red Cross, described the dangers.
He said: "Clearly, where there are dead bodies in fairly stagnant water it creates a breeding ground for disease.
"A priority must be recovering those bodies, for health reasons and for their loved ones."
Mr Schmale compared the aftermath of Hurricane Katrina to the situation in Asia following the tsunami.
He said fears were raised then about epidemics of cholera and typhoid which could claim thousands of lives.
The epidemics never materialised, but Mr Schmale warned people dealing with the destruction in the United States not to be complacent.
He said: "The priority needs to be on providing water and carrying out sanitation work.
"Epidemics are always a danger in these situations and we will always talk about that simply to get the right message across.
"The analogy with the tsunami is a good one because in the first few weeks there was a lot of talk about the potential for disease outbreaks.
"To the best of my knowledge nothing really happened on a noteworthy scale, simply because of the warnings and a lot of effort to prevent it."
The key to dealing with the situation was in acting swiftly to clean up the area and provide fresh water.
He said: "People reacted swiftly and I think that will be the same in the southern USA.
"We don't need to worry so much about the effects of the diseases, the priority has to be to clean up and make sure it does not happen. Put simply, prevention is better than the cure."
Prof Sandy Cairncross, from the London School of Hygiene and Tropical Medicine, said there was a possibility of a cholera outbreak because the bacteria was present in Louisiana's coastal bayous.
He said: "You get epidemics of these diseases because the water supply and sanitation systems are out of action, and the flood water contains diluted sewage." A major epidemic is a "pretty remote possibility" he said, but added that it could not be ruled out.
The mosquito-borne West Nile virus could also cause problems, as the insects breed in dirty water.
The risk of an epidemic developing now depends on the ability of the authorities to cope with the people who have been made homeless.
Prof Cairncross said: "They have to make sure people are accommodated in facilities which are not heavily overcrowded and where the number of people does not overload the sanitation system.
"They must also have a reasonable degree of surveillance for outbreaks of disease, looking for things like leptospirosis, cholera and West Nile to make sure they can nip it in the bud."
He added: "You can't rule an outbreak of disease out. To some extent it depends on how well the US authorities cope with rehousing people and providing adequate facilities."
An outbreak of dysentery has been reported in one of the shelters where people made homeless by Katrina have been housed.
More than 20 people have been taken to hospital after falling ill with the disease at the shelter in Biloxi, Mississippi. - (PA)