Former U.S. public health officials in Washington this week stressed the importance of international cooperation and political independence. They said America's credibility in the global health arena will depend on keeping politics out of science.

Jeffrey Koplan led the Centers for Disease Control and Prevention under President Clinton (1998-2002)

Jeffrey Koplan, who led the Centers for Disease Control and Prevention (CDC) under President Clinton (1998-2002), warned that political involvement in the science of public health undermines the effectiveness of the agency, especially in its international programs.

Koplan was one of five former CDC directors who spoke to public health students Wednesday at George Washington University to mark Public Health Week.

"The closer it is identified with the political process, the harder it is to establish CDC as a non-political health agency with worldwide interests," he said. "And some of that high stature that we've all enjoyed has been eroded a bit. And it serves the political self-interests of this country best when CDC's at that distance."

For example, when they are not politicized, he said national health agencies can talk and share scientific information at a time when politicians might not be able to.

That can be vital when tracking the spread of epidemic disease, said James Mason,

James Mason led the Centers for Disease Control under President Reagan

CDC director under President Reagan (1983-89). He said that's because many of today's disease threats are really global problems.

"You can illustrate this very easily with avian influenza. It won't just affect one country, it'll affect all countries if [it] mutates," he said.

Public health agencies like the Centers for Disease Control have traditionally focused on infectious diseases, such as tuberculosis or malaria or syphilis. Increasingly, however, the focus is broadening to include chronic diseases. And Dr. Mason said that choices that we make - what to eat, how much to exercise, whether to smoke - can have a big impact on the risk of such chronic conditions as heart disease or diabetes or cancer.

"We know that so many of our health problems today are behavior-related," said Mason, "and we still haven't been able to make the dramatic effects and accomplish what could be accomplished if we could just have a bigger influence on how people make decisions and what they do."

David Satcher led the Centers for Disease Control under President Clinton (1993-98)

In some cases, elements of a Western lifestyle can have an impact on health, said David Satcher, CDC director under President Clinton (1993-98). He recalled visits to China, a few years apart. In the mid-1990s, he saw streets full of bicycles and older people doing Tai Chi. When he returned a few years later, he found more people driving, and changes in the traditional diet. A Chinese government report found obesity doubled in the decade from 1992 to 2002.

"So this obesity epidemic, which is now a pandemic, is a major threat to global health," said Satcher. "When it comes to chronic diseases, we don't have a real strategy for dealing with that - not in our country, and certainly not in most other countries."

In looking for international solutions,

William Foege led the Centers for Disease Control under Presidents Carter and Reagan (1977-83)

, who led the CDC under Presidents Carter and Reagan (1977-83), recalled that the late philosopher Will Durant said it would take an alien invasion for humans to put aside their differences.

"Health has the potential to be a surrogate for an alien invasion," Foege asserted. "That's what allowed smallpox to be eradicated. We ought to be more deliberate about doing that, so that SARS and bird flu and so forth - that we use [them] to bring the world together, and we may then become the laboratory that shows how countries can actually work together."

Mostly, public health officials do work well across national boundaries. The smallpox eradication campaign - which Dr. Foege was involved in - is only one example. The ongoing monitoring of avian flu is another.