He has investigated problems with the wastewater-treatment system at the National Science Foundation's McMurdo Station, in Antarctica, and has evaluated the water-recycling systems for the U.S. space program and the Russian MIR space station, where the limitations on volume, weight, and time are severe. ("The issue is how to treat wastewater and get it back quickly so you can drink it. Ideally, you would be able to take a leak and have it right away in your Tang.") Usually, though, Gerba's ventures into microbial-risk assessment, as his field is known, take place closer to home. One might well find him on a given day taking swabs from hotel and motel bathrooms, from picnic tables, from restaurant counters, from office coffee cups, from selected locations inside ordinary houses. He goes door to door collecting sponges and dishrags for analysis, offering people four new ones to replace each old one.
Gerba has written some 400 journal articles on infection and disinfection. His shelves sag under bound volumes of papers, the labels achieving a collective tone of aloof technicality and indeterminate menace. Somewhere among these papers is one called "The Effects of the Discharge of Secondarily Treated Sewage Effluent Into the Everglades Ecosystem" -- his first published work, written at the University of Miami, which gave Gerba his doctorate twenty-five years ago. Gerba is married and has two sons. His wife, Peggy, is an arachnologist. His oldest boy's middle name is Escherichia. Gerba told his father-in-law that it was the name of an Old Testament King.
GERBA'S work first came to my attention a few years ago, when I learned about his investigation of the potential pathogenic hazard posed by disposable diapers in municipal landfills (I was writing a book about garbage at the time), a hazard whose seriousness Gerba eventually discounted. When I stopped by his office recently to say hello, the conversation meandered among a variety of issues. Gerba's observations included the following: The most germ-infested area in one's home is not the bathroom; it is the kitchen. "The kitchen sink is the arrival zone. You are continually bringing germ organisms in there on your food supply, and they colonize your sink and sponges and rags, and grow by the billions overnight. Ten percent of the dishrags we collect door to door contain Salmonella."
The disinfection of public swimming pools is an issue whose time should come. "The average bather puts in fifty milliliters of urine and about a liter of sweat per hour in active swimming." What about children's wading pools -- are they cause for concern? "The chlorine goes so fast with all the kids whizzing in there. We've found potentially disease-causing viruses in every public wading pool we've tested."
Microbes in space vehicles pose unique challenges. "What do you do if there's a leak in the wastewater system? How do you disinfect it? You can't use chlorine in space -- it's too toxic. And what about skin? It flakes off like a powder and after a while becomes a cloud; you need filters to remove it. If we're going to go to Mars, we have to think about this kind of thing."
Russian astronauts have a few other things to think about first. "They were having problems with microbes causing degradation of materials like leather and wood, which they had used in their space station -- can you believe it? Leather and wood? One thing you don't want is for your space station to degrade."
Microbially, the best public restrooms are in hospitals. "If you want the cleanest, pull in to the emergency room. Next are your fast-food restaurants, and the worst are airports and bus stations. The more stalls the better, by the way. And the first stall is the safest, because fewer people use it."
Toilets have an aerosol effect that remains widely unrecognized. "Droplets are going all over the place -- it's like the Fourth of July. One way to see this is to put a dye in the toilet, flush it, and then hold a piece of paper over it. You'll get what we call a commode-o-graph. Every toilet has a characteristic ... well, that's a whole other story."
We strolled for a while around Gerba's laboratories, in a nondescript building that was once used for studies on animal exposure to pathogens; its ventilation system still inhales protectively. One hallway was partly blocked by the equipment that Gerba keeps ready for field expeditions -- pumps, filters, sampling devices, sleeping bags. Refrigerators in the laboratories held hundreds of brightly colored translucent petri dishes in which cell cultures were growing. Some were from Gerba's own experiments. Others had been sent by water utilities that were wondering -- perhaps after a heavy rain flooded some pasturage near the town well or a sleepy technician back-siphoned a sewer line into a water main -- if maybe they had a problem they should be aware of. For the most part bacteria are easily identified by local officials, but many viruses and parasites can be both hard to detect and hard to eliminate. (The parasite Cryptosporidium, to which Gerba devotes much effort, is found in a third of all public water systems and has been a particular scourge among AIDS patients.) One laboratory held a shiny washing machine and dryer, for a new study on the fate of fecal/oral organisms in "gray water" -- the effluent from appliances and bathtubs. Gerba pointed to a plastic bag on top, containing underwear to be washed. "That's mine," he said. "I've asked all the graduate students to bring theirs in too." In another lab stood a trio of commercial water-purification devices, the freshly processed water percolating into clear blue plastic tubs. Gerba's young technicians were testing the manufacturer's claim that the system would remove dangerous pathogens. I asked one technician what she had put into the water to test the system. She replied, "Cholera." Another technician said, "Tomorrow we'll hit it with polio."
BACK in his office Gerba explained that run-of-the-mill household transmission of ordinary disease is a problem that will come increasingly to the fore, and that microbial-risk assessment will increasingly become part of our lives. One reason is the food supply. More and more produce is imported, and the water used to grow it is often heavily contaminated. A second, more significant, reason is demographic. "If you look at the general population," Gerba said, "maybe only one in a thousand who are infected will die from an E. coli infection. If you look at the elderly, one in ten who are infected may die from it. Of course, the elderly population is increasing. We also have many more immunocompromised people -- not just people with AIDS but also cancer patients receiving chemotherapy, a million of them. Hospital stays in general are getting shorter -- they want to get you out before you get an infection, actually. And they put you back into an environment where there are a lot of organisms that can take advantage of you. Throw in pregnant women, neonates, people on heavy antibiotic therapy, diabetes patients -- already we're up to a fifth of the U.S. population. And we're discovering more and more pathogens all the time, and giving them more opportunities. Legionella becomes capable of causing disease only when it grows at high temperatures, above twenty degrees centigrade. It was a nonproblem until we had hot tubs and cooling towers.
"Microbes have crept up the list. They are now the third leading cause of death in the United States. In 1980 they were the fifth. Sometime in the next century they will be on top."
Before I left his office, Gerba gave me some bags of bacteria-resistant sponges and some flasks of kitchen disinfectant -- primitive yet effective talismans that can ward off much evil. They cannot quite ward off the memory of a verse from Chronicles: "For we are powerless against this great multitude that is coming against us." The words were spoken by Jehoshaphat -- another of those Old Testament Kings.
Cullen Murphy is the managing editor of The Atlantic and the author of Just Curious (1995), a book of essays. He writes the comic strip Prince Valiant.
Photograph by John Florence
The Atlantic Monthly; September 1997; Something in the Water; Volume 280, No. 3; pages 26-28.