From Prof Debarati Guha-Sapir.

Sir, Instant reactions after earthquakes typically predict epidemics, but in fact normal wave action tends to dilute the bacterial load of diseases such as cholera, and washes away mosquito breeding sites for weeks or even months. This gives a useful window of opportunity to target assistance properly.

Right now, the main health hazards threatening poor communities are those related to exposure. Acute respiratory disease and life-threatening drops in nutritional status in already malnourished children may take many more lives. The longer people live in unsanitary conditions, the higher the risk of disease transmission.

Lack of sanitation and hygiene among survivors in overcrowded temporary shelters are a prime source of diarrhoea and gastroenteritis. But fears about drinking water contaminated by decaying cadavers are overstated. It can produce effects such as food poisoning after eating rotting meat but a survivor defecating close to the water is more of a hazard for others than a dead body. Viruses, parasites and bacteria all prefer live hosts.

So humanitarian aid must focus on standard public health measures such as sanitation, surveillance of tsunami victims in shelters by aid groups, and chlorinated water for all.

Remember demographics: the region affected by the tsunami has a young population, and resumption of care for its hundreds of thousands of pregnant women, for example, must rank high on the list of priorities.

And let us think now about the many households that have lost men at sea and are headed by women who will struggle without targeted help.

If we do not do so, the effects of this disaster will be life-threatening long after the spotlight moves elsewhere.

Debarati Guha-Sapir, Director, World Health Organisation Collaborating Centre for Research on Epidemiology of Disasters, Professor, Epidemiology Unit, University of Louvain School of Public Health, 1200 Brussels, Belgium