The waves hit some of the poorest countries on earth — where public health systems, already weak, are now overwhelmed.
"There is a chance that we could have at least as many dying from communicable diseases as we've had dying from the tsunami," says Dr. David Navarro with the United Nation's World Health Organization.
The biggest danger is the lack of sanitary drinking water — contamination by sea water and human waste.
"Once the water supply gets contaminated, especially with sewage, then water-borne diseases like cholera and dysentery can become rampant," says Dr. Irwin Redlener, president and co-founder of the Children’s Health Fund.
Other fears: Exploding mosquito populations could bring outbreaks of malaria and dengue fever, while the millions of homeless face potential epidemics of flu and other respiratory infections.
To try to lessen the disease threat, U.N. officials are working to coordinate one of the largest and most logistically-challenging peacetime relief efforts in history.
- Chlorine tablets and other means of providing fresh water;
- Equipment to bury dead humans and animals;
- Mobile clinics to treat the injured;
- Antibiotics for disease outbreaks;
- Shelter for the homeless.
How critical is the effort? In 1976 an earthquake in Guatemala killed 23,000 people. But officials estimate three-times that many died from disease outbreaks that followed.
By contrast, Hurricane Andrew in 1992 — one of the largest natural disasters to strike the U.S. — destroyed hospitals and knocked out power, water and sanitation facilities, but the response was rapid and immense.
"Almost within hours and certainly within days we had reestablished a health care infrastructure in southern Florida and very few lives were lost as a consequence of that," says Dr. Redlener.
The speed with which relief supplies arrive in the wake of the tsunami will decide whether thousands more live or die.