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An infectious discovery

The Nobel in medicine honors a paradigm shift: It may be a bug, not your bad habits, that's killing you.

October 08, 2005|Madeline Drexler

BARRY MARSHALL won this year's Nobel Prize in medicine for his discovery that peptic ulcers were caused by an infection -- not stress, smoking or alcohol. The nearly mythical story of how he proved this has been widely told this week: He swallowed a noxious solution of beef broth and bacteria, giving himself severe gastritis.

But there's a larger story inside the jaunty Australian's brash discovery in the early 1980s. Along with fellow laureate J. Robin Warren, Marshall opened up a line of research that has utterly changed the way scientists think about infection and illness. Simply put: Many deadly, chronic ailments typically blamed on lifestyle -- heart disease, cancer, diabetes and others -- may actually be triggered by viruses and bacteria. If true, the repercussions are almost beyond imagining.

When we think of emerging infections, we usually think of sudden doom: avian flu, SARS, Ebola fever. But after Marshall and Warren shed light on the role of Helicobacter pylori in ulcers, it became clear that countless other emerging pathogens also may be quietly lurking in our bodies, causing not lethal scourges but familiar and insidious afflictions.

In the years since Marshall's and Warren's debut scientific papers were published, researchers have proved that infections cause cervical cancer, Kaposi's sarcoma (a malignant complication of AIDS), a childhood form of obsessive-compulsive disorder (from strep), most liver cancer and many cases of paralytic Guillain-Barre syndrome (from food-borne infections). Further, scientists strongly suspect that infections provoke such ills as atherosclerosis, multiple sclerosis, juvenile diabetes, Crohn's disease, gallstones, schizophrenia and even many cases of premature birth (because of untreated gum disease in the mother).

A quarter of a century ago, the very notion that these conditions were infectious in origin would have been laughed out of the room -- as were Marshall's and Warren's first claims that bacteria cause ulcers.

HOW DO microorganisms set in motion the slow-forming illnesses we usually blame on bad diet, lack of exercise and other lifestyle sins? No one knows for sure. But consider that our bodies contain at least 10 times more bacterial cells than human ones, making us walking Petri dishes and blurring the line between where microbes end and humans begin. Scientists are only starting to realize how much they don't know about what's living in and on modern Homo sapiens. Moreover, it's estimated that less than 1% of all bacterial species have been identified. Only a tiny fraction of bacteria and viruses can be cultured with standard lab methods.

In probing this dearth of knowledge, scientists are also realizing that the one germ/one disease idea -- the cornerstone of 19th-century germ theory -- is too simple to account for all the interactions of our bodies' teeming microbial hordes. Yes, mosquito-transmitted parasites cause malaria, rod-shaped bacteria cause tuberculosis and Rhinoviruses cause the common cold. But in addition, scientists now believe that the bacteria and viruses unobtrusively inhabiting our bodies are working covertly and in concert to bolster or undermine our health.

Because of Marshall's and Warren's research, ulcers are no longer treated with surgery but with antibiotics. If infections prove to be the culprit behind a host of other chronic illnesses, doctors might be able to use vaccines and antibiotics to prevent and cure these maladies, rather than relying on toxic last-hope drugs or hard-to-follow lifestyle advice. On the other hand, the success story of antibiotics and ulcers might turn out to be an exception. Vaccines or antibiotics may not work for MS or plugged coronary arteries, or might give rise to such untoward complications as autoimmune disease or antibiotic resistance.

In other words, it's impossible to know just where this breakthrough will lead or how it will be applied. What's important is that Marshall and Warren helped reveal a new way of looking at disease -- a "new germ theory," as it's been called, enthusiastically taken up by researchers around the world. The Nobel committee praised the pair for challenging "prevailing dogmas with tenacity and a prepared mind." In doing so, it drew comparisons with Louis Pasteur, the 19th-century French chemist and bacteriologist who stands as one of the giants of the original germ theory. One hundred years from now, the story of a cheeky Australian doctor's foul-tasting experiment will still be told. But the real story of science is constantly unfolding.

MADELINE DREXLER is a Boston-based journalist and author of "Secret Agents: The Menace of Emerging Infections" (Penguin, 2003).

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