Early estimates indicate 20 percent of children in the most devastated areas are suffering from diarrhea, and the situation could worsen, said Osamu Kunii, UNICEF's chief of health and nutrition in Yangon, Myanmar's largest city.

"Most of the area is covered by dirty water," he said. "There's a lot of dead bodies and they have very poor access - sometimes no access - to clean drinking water or food."

Water purification tablets are unlikely to help because much of the water supply has been contaminated by saltwater, he said.

It was unclear how many people may have malaria, but the mosquito-borne disease is endemic to Myanmar's Irrawaddy delta, said Poonam Khetrapal Singh, deputy director of the World Heath Organization's Southeast Asia office in New Delhi. She said 10,000 mosquito nets were being sent in.

"Safe water, sanitation, safe food. These are things that we feel are priorities at the moment," Singh said.

Cyclone Nargis lashed Yangon along with the country's major rice-growing region Saturday, killing tens of thousands.

The WHO team in Myanmar is working to assess the situation, and a few international technical experts are making their way into the country, Singh said.

"It reminds me of the tsunami when every day the figures kept rising, and that's really the pattern here," she said, referring to the 2004 Asian tsunami, which killed nearly 230,000 people.

Kunii said the situation in Myanmar is worse in some ways because more people suffered severe injuries from strong winds, high tides and flooding. And he noted that after the tsunami, food and water could be obtained from inland areas that were not hit by the killer waves.

"This time it is quite difficult because most of the areas are quite remote and difficult to access," Kunii said. "We are trying our best."

Tens of thousands of people die every year in Myanmar, also known as Burma, from tuberculosis, AIDS and diarrhea. Malaria alone kills about 3,000 people annually in the country.

In 2000, WHO ranked Myanmar's health system as the world's worst after war-ravaged Sierra Leone. There are hospitals, but most people cannot afford treatment because about 90 percent of the population lives on just $1 a day.

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Margie Mason covers medical issues for The Associated Press across the Asia-Pacific. She is based in Hanoi, Vietnam.

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