BANGKOK, Thailand (AP) -- Preventing a disease disaster in Myanmar is now a "race against time," as many impoverished victims still await help a week after the brutal cyclone, experts warned Saturday.

Reports of diarrhea and skin problems already have surfaced, and health officials fear waterborne illnesses will emerge because of a lack of clean water, along with highly contagious diseases such as measles.

Children, especially those orphaned by the storm, face some of the greatest risks.

Cyclone Nargis left more than 60,000 people dead or missing. The U.N. estimates that at least 1.5 million people have been severely affected in the military-run country, which has one of the world's worst health systems.

"The fact that there are people we still haven't gotten to is very distressing to all of us. We don't know how many that is," Tim Costello, president of the aid agency World Vision-Australia, said by telephone from Myanmar's largest city, Yangon. "The people are all exposed to the elements, and they are very, very vulnerable. It's a race against time."

In the badly hit town of Labutta, family members were forced to use rusty sewing needles to close wounds at a hospital where no doctors or supplies were visible. One man lay dying from a lack of care after his foot was cut off in the cyclone.

The World Health Organization has reported children suffering from upper respiratory diseases, and with next week's forecast calling for rain, there was yet another urgent reason to move quickly.

Fears of mosquito-borne diseases such as malaria and dengue fever, which are endemic to the area, also have heightened. However, outbreaks would not be expected for another week or longer because the mosquitoes need time to breed in stagnant water left from the storm, said Osamu Kunii, UNICEF's chief of health and nutrition in Yangon.

Cholera remains another concern, but there have been no diagnosed cases. Kunii said Myanmar's health ministry also agreed to start a mass vaccination campaign against measles.

"Once those diseases start, it's very hard to control," he said, adding that food and water were reaching more survivors but not everyone.

Some victims have been drinking whatever water is available, with many freshwater sources contaminated by saltwater or littered with decaying human bodies and animal carcasses. UNICEF has reported diarrhea in up to 20 percent of the children living in some badly affected areas. Injuries suffered from high winds and debris that struck people during the storm also remain a problem, with many suffering from raw open wounds.

Costello said frustration with the military junta's slow response and restrictions placed on humanitarian aid entering the country has reached a critical point.

"The government initially admitted that this was bigger than them. But now they have said, `While we need more aid, we are the military. We made this nation, and we're very proud of it and we can cope with it,'" Costello said. "It is absolutely clear that they can't."

Tens of thousands of people die every year in Myanmar, also known as Burma, from diseases such as tuberculosis, AIDS and diarrhea. Malaria alone kills about 3,000 people annually in a country where medical care is too expensive for most people to afford. In 2000, WHO ranked Myanmar's health system as the world's worst after war-ravaged Sierra Leone.

About 90 percent of the population lives on just $1 a day. Millions also go hungry, with a third of Myanmar's children estimated to be malnourished.

"It is an unfortunate reality that this storm hit a country that already had this very marginal ... health system," said Dr. Chris Beyrer, an epidemiologist from Johns Hopkins University who has worked extensively in Myanmar. "When you have malnourishment with infectious diseases, the fatality rates go up."

He co-authored a critical report published last year that found the government spends only about 3 percent of its annual budget on health, compared to 40 percent on the military. The country's ailing health system combined with the junta's paranoia of foreigners is a cocktail for an even bigger disaster in the storm's aftermath, Beyrer said.

"I think when it comes to this regime, nothing is that surprising," he said by telephone from Maryland. "The fundamental issue is access. This is what we were arguing about for HIV/TB and malaria control five years ago - that it is access and that the international community is ready to help."