Caution: Killing Germs May Be Hazardous to Your Health

Hunter needed eight operations over the next week to drain her infections, and an intravenous drip of two powerful new antibiotics, Zyvox and Cubicin. She did survive, and is home now, but her lung capacity is at 35 percent of normal. "We are seeing more infections, and more severe infections" with the USA300 strain, says Dr. Jaime Fergie, who treated her at Driscoll. In many cases, there's no clue as to how the infection was contracted, but a study Fergie did in 2005 of 350 children who were seen at Driscoll for unrelated conditions found that 21 percent of them were carrying MRSA, mostly in their noses. Then all it may take is a cut … and an unwashed hand.

And there are plenty of unwashed hands out there; Gerba claims that only one in five of us does the job properly, getting in all the spaces between the fingers and under the nails and rubbing for at least 20 seconds. Americans have been obsessed with eradicating germs ever since their role in disease was discovered in the 19th century, but they've been partial to technological fixes like antibiotics or sanitizers rather than the dirty work of cleanliness. Nancy Tomes, author of "The Gospel of Germs," believes the obsession waxes and wanes in response to social anxiety—about diseases such as anthrax, SARS or avian flu, naturally, but also about issues like terrorism or immigration that bear a metaphoric relationship to infection. "I can't protect myself from bin Laden, but I can rid myself of germs," she says. "Guarding against microbes is something Americans turn to when they're stressed." The plastic squeeze bottle of alcohol gel, which was introduced by Purell in 1997, is a powerful talisman of security. Sharon Morrison, a Dallas real-estate broker with three young daughters, estimates she has as many as 10 going at any time, in her house, her car, her purse, her office and her kids' backpacks. She swabs her grocery cart with sanitizing wipes and, when her children were younger, she would bring her own baby-seat cover from home and her own place mats to restaurants. Sales of Purell last year were $90 million, so she's clearly not alone. There's no question it kills germs, although it's not a substitute for washing; the Centers for Disease Control Web site notes that alcohol can't reach germs through a layer of dirt. Alcohol gels, which kill germs by drying them out, don't cause the kind of resistance that gives rise to superbugs like MRSA. But they're part of the culture of cleanliness that's led to a different set of problems.

In terms of infectious disease, the environment of the American suburb is unquestionably a far healthier place than most of the rest of the world. But we've made a Faustian bargain with our antibiotics, because most researchers now believe that our supersanitized world exacts a unique price in allergies, asthma and autoimmune diseases, most of which were unknown to our ancestors. Sachs warns that many people drew precisely the wrong conclusion from this, that contracting a lot of diseases in childhood is somehow beneficial. What we need is more exposure to the good microbes, and the job of medicine in the years to come will be sorting out the good microbes from the bad.

That's the goal of the Human Microbiome Project, a five-year multinational study that its advocates say could tell us almost as much about life as the recently completed work of sequencing the human genome. One puzzling result of the Human Genome Project was the paltry number of genes it found—about 20,000, which is only as many as it takes to make a fruit fly. Now some researchers think some of the "missing" genes may be found in the teeming populations of microbes we host.

And the microbe project—which as a first step requires sampling every crevice and orifice of 100 people of varying ages from a variety of climates and cultures—is "infinitely more complex and problematic than the genome," laments (or boasts) one of its lead researchers, Martin Blaser of NYU Medical School. Each part of the body is a separate ecosystem, and even two teeth in the same mouth can be colonized by different bacteria. In general, researchers know what they'll find—Escherechia (including the ubiquitous microbial Everyman, E. coli) in the bowel, lactobacilli in the vagina and staphylococcus on the skin. But the mix of particular species and strains will probably turn out to be unique to each individual, a product of chance, gender (men and women have different microbes on their skin but are similar in their intestines) and socioeconomic status and culture. (Race seems not to matter much.) Once the microbes establish themselves they stay for life and fight off newcomers; a broad-spectrum antibiotic may kill most of them but the same kinds usually come back after a few weeks. The most intriguing question is how microbes interact with each other and with our own cells. "There is a three-way conversation going on throughout our bodies," says Jane Peterson of the National Human Genome Research Institute. "We want to listen in because we think it will fill in a lot of blanks about human health—and human disease."

The vast majority of human microbes live in the digestive tract; they get there by way of the mouth in the first few months of life, before stomach acid builds to levels that are intended to kill most invaders. The roiling, fetid and apparently useless contents of the large intestine were a moral affront to doctors in the early years of modern medicine, who sought to cleanse them from the body with high-powered enemas. But to microbiologists, the intestinal bacteria are a marvel, a virtual organ of the body which just happens to have its own DNA. Researchers at Duke University claim it explains the persistence of the human appendix. It serves, they say, as a reservoir of beneficial microbes which can recolonize the gut after it's emptied by diseases such as cholera or dysentery.