With chaos on the ground in Myanmar and no reliable sources of information, Maryland disaster experts say it's no surprise that casualty counts from the cyclone that struck the country can range from 22,500 to 100,000.
The remote nature of the devastated area and government restrictions on Western relief organizations mean that very little reliable news about deaths or the plight of survivors has appeared, said W. Courtland Robinson, deputy director of the Center for Refugee and Disaster Response at the Johns Hopkins Bloomberg School of Public Health.
"You start with these very, very rough estimates, and that's usually from somebody on the ground who may not have the best information. Then you work from there," said Robinson, who may soon visit Myanmar as part of the relief effort.
The Myanmar government's official death toll is 22,5000, but an American diplomat in Myanmar, Shari Villarosa, said in news reports that the toll could rise to 100,000 if international aid doesn't arrive soon.
Such wide-ranging estimates are not unusual in the first days after a natural disaster, experts say. In the day or so after the 2004 tsunami struck Southeast Asia, initial estimates were that 5,000 to 10,000 had perished, Robinson recalled. It actually killed 150,000.
Relief organizations are traditionally a major source of early information about death and survival rates. In Myanmar, the cyclone hit hardest in the remote Irrawaddy delta region, but the military government has restricted access of relief agencies to the area's 3 million residents. Without medical help and clean water, experts say, there's a risk of cholera and other diseases.
"The population is large, and it's a relatively inaccessible area, even under normal conditions," said Robinson, who flew to Indonesia a few days after the 2004 tsunami to track the numbers of dead and missing.
Robinson is studying the displacement of the population and the numbers of refugees who returned to their homes after the 2004 tsunami. He is also working with researchers at Columbia University, using satellite imagery and other data, to estimate the death toll in Myanmar.
"I would say, at this point, I would be very interested in going there," he said.
It took several months to come up with an authoritative death toll after the 2004 tsunami in Indonesia - and it may take as long in Myanmar, experts say.
"It depends on how transparent the government is, and so far they haven't been," said Gregg Greenough, who tracks displacement after disasters as research director of the Harvard Humanitarian Initiative.
Researchers trying to estimate casualties after a disaster use satellite imagery and evolving computer models that are based on population estimates. But the Myanmar military government, which has frosty relations with the Bush administration, may prove to be an obstacle there as well, officials say.
"One of the most important things is to have a sense of underlying populations - who was there beforehand - and that usually comes from a census or government records of some sort. But if they had a census or registration of births or deaths, they are not likely to share it," Greenough said.
When a region is devastated by a hurricane, flood or series of storms, the nature of the terrain, the amount of precipitation that fell and factors such as the population's economic status and housing stock also become important.
Poorer populations usually die at higher rates because they are less able to get out of harm's way, experts say.
"The biggest issue is displacement. You have to know how many people were in the area, on the ground beforehand, and then you have to go to the area and ask, 'How many people were in your house and how many people got out safely?'" Greenough said.
Initial reports can also be misleading, experts say.
One report on a U.N. Web site estimated that 10,000 people were killed in the town of Bogalay, population 190,000. But it's not necessarily accurate to extrapolate that high casualty rate to the whole Irrawaddy population of 3 million when there's no way to know whether Bogalay's death count is accurate or whether the town was harder hit than other communities.
"Sometimes you can kind of extrapolate from what you know happened to some of a population, but that doesn't always work," Robinson said.
It is essential for researchers to collect reports from survivors in order to produce authoritative casualty counts, which in turn can galvanize world support and aid to a stricken area, experts say.
Robinson said scientific analysis of casualties helps develop policies that will minimize losses in future disasters - and improve responses.
"Mortality gives you a picture not only of who perished, but who is most at risk," he said.