At Home - Bill Bryson [134]
The most celebrated germ expert in the world is almost certainly Dr. Charles P. Gerba of the University of Arizona, who is so devoted to the field that he gave one of his children the middle name Escherichia, after the bacterium Escherichia coli. Dr. Gerba established some years ago that household germs are not always most numerous where you would expect them to be. In one famous survey he measured bacterial content in different rooms in various houses and found that typically the cleanest surface of all in the average house was the toilet seat. That is because it is wiped down with disinfectant more often than any other surface. By contrast the average desktop has five times more bacteria living on it than the average toilet seat.
The dirtiest area of all was the kitchen sink, closely followed by the kitchen counter, and the filthiest object was the kitchen washcloth. Most kitchen cloths are drenched in bacteria, and using them to wipe counters (or plates or breadboards or greasy chins or any other surface) merely transfers microbes from one place to another, affording them new chances to breed and proliferate. The second most efficient way of spreading germs, Gerba found, is to flush a toilet with the lid up. That spews billions of microbes into the air. Many stay in the air, floating like tiny soap bubbles, waiting to be inhaled, for up to two hours; others settle on things like your toothbrush. That is, of course, yet another good reason for putting the lid down.
Almost certainly the most memorable finding of recent years with respect to microbes was when an enterprising middle school student in Florida compared the quality of water in the toilets at her local fast-food restaurants with the quality of the ice in the soft drinks, and found that in 70 percent of outlets she surveyed the toilet water was cleaner than the ice.
What is perhaps most remarkable about all these multitudinous life forms is how little we sometimes know about them—and how recently what we do know has been learned. Bed mites weren’t discovered at all until 1965, even though millions of them exist in every bed. As late as 1947, a medical correspondent for The New Yorker could write: “Mites are only infrequently found in this country and until recently were practically unknown in New York City.” Then, in the late 1940s, residents of an apartment complex called Kew Gardens in Queens, New York, began sickening in large numbers with flulike symptoms. The malady was known as “the Kew Gardens mystery fever” until an astute exterminator noticed that mice were also getting sick and discovered on close inspection that tiny mites living in their fur—the very mites that were supposed not to exist in America in large numbers—were transmitting rickettsialpox, a kind of spotted fever, to apartment dwellers.
Similar degrees of ignorance have long applied to many larger creatures, not least one of the most important and least understood of all animals that are sometimes found in modern houses: bats. Hardly anybody likes bats, which is truly unfortunate because bats do much more good than harm. They eat enormous quantities of insects, to the benefit of crops and people alike. Brown bats, the most common species in America, consume up to six hundred mosquitoes per hour. Tiny pipistrelle bats—which weigh no more than a small coin—vacuum up three thousand insects apiece in the course of