India flood: disease threat

The cholera bacterium can cause serious disease

Many illnesses flourish during and in the wake of severe flooding, particularly in hot countries. BBC News Online examines those most likely to strike.

Cholera and dysentery

Flooding forces huge populations into small areas - sanitation facilities there often cannot cope, and water supplies may become tainted.

The prime threat is likely to come from cholera, an infection of the gut which causes chronic diarrhoea and vomiting.

This can lead to severe dehydration and, in extreme cases, death. It is caused by contaminated water and food.

It is at its most deadly following natural disasters such as floods because treatment facilities are not available.

Other conditions likely to be rife include dysentery, which causes nausea, loose stools, weight loss, abdominal tenderness and occasional fever.

Rarely, the parasite responsible for dysentery invades the body beyond the intestines and causes a more serious infection.

Danger from E coli is also likely to increase - E coli symptoms can range from mild diarrhoea to abdominal cramps and blood in the stools.

Some E coli sufferers also suffer from a complication - haemolytic uremic syndrome (HUS), which kills red blood cells and can cause kidney failure and even death.

Malaria

The receding waters leave marshes which are the ideal breeding ground for mosquitoes and other insects.

This can lead to an increase in the prevalence of insect-borne diseases such as malaria and dengue fever.

Most people survive a bout of malaria after a 10-20 day illness. The symptoms include high fever, followed a few hours later by chills. Two to four days later, this cycle is repeated.

The most serious forms of the disease can affect the kidneys and brain and can cause anaemia, coma and death.

What can be done?

Cholera and dysentery can be treated with antibiotics, but the bacteria are increasingly resistant to the drugs.

The main response to both diseases is rehydration treatments. The problem will be getting supplies - and clean drinking water - to the people who need help.

Setting up water filtration systems to eradicate water-borne diseases will be important.

Bed nets impregnated with anti-malarial chemicals will help stop transmission of the disease.

What will be the timescale?

Professor Bohumil Drasar, professor of bacteriology at the London School of Hygeine and Tropical Medicine, said: "Cases which are water-borne will be starting now. Once the water goes down, it will have affected mosquito breeding - there will then be transmission of malaria and possibly dengue fever."

He said emergency aid was needed immediately, but a long term effort, lasting at least six months, would be required to bring disease under control.

The final effect of the flood may be to disrupt other public health measures, such as vaccination programmes.

This may have an even longer term effect on the population.