Public health officials warn survivors of Sunday's tsunami face a grave danger, death and disease caused by filthy drinking water.  Officials say rescue teams are focusing their attention on getting potable water to survivors of the massive undersea earthquake to keep the population of the affected areas from falling victim to its aftermath.

The United Nations and the U.S. Agency for International Development (USAID) have deployed relief teams to the 11 Asian countries devastated by Sunday's tsunami.  The hardest hit countries have been Indonesia, Sri Lanka, India, Thailand and the Maldives.  Malaysia, Myanmar, Bangladesh, Somalia, Tanzania, Seychelles and Kenya are also assessing damage from the massive Indian Ocean earthquake.

At a State Department briefing, USAID administrator Andrew Natsios says the primary focus of relief effort is sanitation.

"What's happened basically is the water and sewage systems are now combined because of the water surges that took place and the destruction that followed, and as a result people are drinking sewage water,? he explained.  ?And that will substantially increase the risk of communicable disease and diarrheal disease which could kill many people in epidemics if they get out of control."

Mr. Natsios says U.S. response teams and private organizations in other countries are trying to get clean water to as many survivors as possible.

World Health Organization official David Nabarro says health officials expect the first wave of sickness to be cholera and diahhreal disease, which he says will strike in about one week. 

"Then, after a few weeks, we're going to expect to see a rise in vector transmitted, that's insect-transmitted, diseases like malaria and dengue," he said.

That's because mosquitos flourish in still water.  Speaking on NBC's Today show, Dr. Nabarro says contrary to popular belief, dead bodies are not a source of disease.

"Historically, that's been said and been quoted frequently,? he added.  ?But our experience is that dead bodies are unsightly and unpleasant but not a major cause of disease.  The disease is caused as I've said by contaminated water, lack of food, inadequate sanitation, insect borne conditions, overcrowding and those are the issues we must concentrate on now."

Dr. Nabarro was asked what the message should be to survivors of the disaster who want to bury loved ones in mass graves.

"It would say, 'Yes, of couse, please bury the dead properly in a way that is appropriate.  But you're not doing it primarily because of the spread of disease.  If you want to concentrate on avoiding the spread of disease, please concentrate on ensuring access to clean water and adequate food and proper shelter.'  And possibly there may be five million people who have been put at risk after they've survived these terrible tragedies.  Please do everything possible they don't have the further tragedy of disease related death over these next few weeks," he noted.

The United Nations is expected to make an appeal for assistance within the next week.