The Venezuelan flood and mudslide disaster could be compounded by the outbreak of life threatening disease among survivors.

The United Nations estimates that 15,000 people are dead, with another 30,000 unaccounted for.

But the Pan American Health Organization (PAHO) has warned that there is a heightened risk of disease in the country, and that this could put many others at risk.

The major problem is the breakdown of normal sanitary conditions. This can provide an environment for outbreaks of infectious diseases or diseases already endemic in a country.

The huge number of people who have been displaced is also likely to be factor.

Tens of thousands of people are abandoning the coastal states hit hardest by the flooding and are converging on the already over-stretched refugee centres in the capital, Caracas.

The close proximity of many people living in cramped, insanitary conditions is an ideal breeding ground for disease.

The presence of unburied dead bodies can also spread disease, although this is likely to be a less important factor.

Cholera

The spread of cholera is one of the main dangers following any natural disaster.

Cholera is an acute infection of the gut which causes chronic diarrhoea and vomiting.

This can lead to severe dehydration and, in some extreme cases, death.

However, most people who are infected by the bug do not become ill and 90% of those who do are only mildly or moderately ill.

Cholera is spread by contaminated water and food. Sudden outbreaks, such as those which follow a disaster, are usually caused by a contaminated water supply.

The bug is most deadly when it arrives unexpectedly - as in times of disaster - because there are often no facilities for treatment or because people cannot get treatment in time.

In communities which are unprepared for a cholera outbreak, up to 50% of people who become seriously ill may die.

Cholera can be effectively treated with oral rehydration salts and antibiotics.

Containing a cholera outbreak involves ensuring there are proper sanitation methods for disposing of sewage, an adequate drinking water supply and good food hygiene.

Food should be cooked thoroughly and should not be contaminated by contact with raw foods, flies or dirty surfaces.

The only cholera vaccine that is widely available is less than 50% effective and only lasts up to six months.

There are two other vaccines that protect against one strain of cholera for a short period.

Relief effort

PAHO has set aside $25,000 to deal with the health problems and has mobilised a team of epidemiologists, health services experts, and sanitary engineers to work with local government authorities.

Top priorities include monitoring potential outbreaks of disease, sanitary disposal of dead bodies and setting up vaccination programmes for those at high risk of disease.

Establishing basic sanitation and water supplies is also an urgent requirement.

PAHO will also set up a mental health programme for people struggling to cope with the trauma of losing loved ones and their homes.