Infectious diseases don't yield to easy solutions because both the players and the playing field are constantly changing. Globalization has tilted the playing field, at least temporarily, in favor of the pathogens. That's because our opponents have the ability to constantly change "uniforms" by mutating.

Even so, infectious-disease specialists know there are things that can be done. There are two approaches. One uses incremental change—new vaccines or new public-health strategies, for instance. These methods have quelled some of nature's worst killers, most notably smallpox. The other approach looks at the world as an interconnected whole and attempts to formulate a big-picture strategy. Both are being advanced at Dartmouth.

The incremental approach

A traditional tactic is to take a single problem related to a single disease and try to solve it. When the disease is AIDS, the potential payoff is enormous. Scientists know HIV does its damage in part by unhinging bits of the immune system. That leaves sufferers open to a wide variety of illnesses that can infect them and ultimately kill them.

Tuberculosis (TB) is among the worst of these opportunistic killers. That's because the virus that causes AIDS attacks cells in the immune system that are critical to controlling TB, says Fordham von Reyn, M.D., chief of infectious disease at DHMC. This makes anyone infected with HIV far more likely to develop TB. Von Reyn is the principal investigator of a four-year study of the efficacy of a tuberculosis vaccine booster for HIV-positive individuals. The vaccine, now being tested in Tanzania, is designed to supplement the TB vaccines that are routinely given to African children and add an additional layer of protection for the huge number of HIV-infected Africans.

The production of flu vaccines is another arena where new strategies are being sought. "We need a different system," says John Modlin, M.D., former chair of the federal Advisory Committee on Immunization Practices and DMS's chair of pediatrics. "I'm not sure I have the

"We want to be able to buy strawberries in New York in January," says DMS's Sharon McDonnell.

answer. But what is likely to be required is a high degree of public-private partnership, which offers incentives to bring private vaccine manufacturers into the marketplace. Since vaccines are much more expensive to produce than drugs, there isn't a strong incentive to make vaccines. Many, if not most, of the vaccine makers have dropped out of the market."

Imported foods are another source of disease. Public-health specialists say this problem can be mitigated by watching—or washing very well—what we eat, particularly fruits and vegetables. Some imported fruits, for example, carry parasites that can produce severe gastrointestinal illness in people with compromised immune systems, according to Sharon McDonnell, M.D., M.P.H., an adjunct associate professor of community and family medicine at DMS and an instructor in the School's M.P.H. program. "Imports are how we get much of our fruit in the off-season," she says. "We want to be able to buy strawberries in New York in January. But we have certain expectations of how food will be handled. Those expectations may not be met with imported food."

The systems approach

The other approach to global disease is systems thinking, which looks at the whole picture, not just its component parts. Paul Batalden, M.D., the resident systems thinker at DMS, explains that humans "are a fundamental force in nature. We are one of the reasons for globalization and disease. Therefore, if we are part of the problem, we have to change what we're doing. You can't keep doing what you're doing and muck your way through. But if you begin by understanding that we're all part of the

problem, you begin to see options that you haven't seen before.

"The temptation is to say some single answer will solve the problem, but that won't work. We must continually change what we're doing. You have to recognize that as you take steps to deal with global disease, the disease organisms are interacting with the steps you're taking. It's part of living systems that they morph; bugs have the capacity to change." To deal with mutations, Batalden suggests we think like a member of a jazz quartet, where successful improvisation requires that all the players work together. "A good jazz player knows how he will sound in conjunction with the other members. And he has to listen very carefully to what they are doing."

Batalden says we also need to delve deeply enough to avoid solutions that may at first glance look appealing but that will ultimately fail. So in the case of globalization and disease, we can't shut down air travel, he says. But there are other options. "What if we made an investment in the vitality of our population by keeping people healthier? If they were healthier, they would be less likely to succumb from disease." (And, he adds, a healthier populace would help tame the spiral of health-insurance costs.)

Systems thinking evolved from the work of industrialists who wrestled with complex issues and often came up with contrarian solutions. In 1914, for instance, Henry Ford introduced an unheardof $5-a-day pay scale at a time when other carmakers were trying to pay workers as little as possible. But Ford's move attracted the best workers and cut employee turnover. And with their fatter paychecks, Ford workers made enough to afford Ford cars. W. Edwards Deming came along later and developed a theory of effective workplaces that he called total quality management.

Batalden has been a pioneer in applying such thinking to medicine—especially globalization and infectious disease. "Every system is perfectly designed to get the results it gets," is Batalden's mantra. "If we don't like the results, and we don't redesign the system to produce different results, then we've deluded ourselves."