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Delve deeper into hot topics featured in NGM's November Geographica and Who Knew? with help from Resources. Click on a link, pick up a periodical, browse through a book, and explore!
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Can germs keep us healthy?
Whenever a new disease appears somewhere on our planet, experts invariably pop up on TV with grave summations of the problem, usually along the lines of, "We're in a war against the microbes"—pause for dramatic effect —"and the microbes are winning."
War, however, is a ridiculously overused metaphor and probably should be bombed back to the Stone Age.
Paul Ewald, a biologist at the University of Louisville, advocates a different approach to lethal microbes. Forget trying to obliterate them, he says, and focus instead on how they co-evolve with humans. Make them mutate in the right direction. Get the powers of evolution on our side.
Disease organisms can, in fact, become less virulent over time. When it was first recognized in Europe around 1495, syphilis killed its human hosts within months. The quick progression of the disease—from infection to death—limited the ability of syphilis to spread. So a new form evolved, one that gave carriers years to infect others.
For the same reason, the common cold has become less dangerous. Milder strains of the virus—spread by people out and about, touching things, and shaking hands—have an evolutionary advantage over more debilitating strains. You can't spread a cold very easily if you're incapable of rolling out of bed.
This process has already weakened all but one virulent strain of malaria: Plasmodium falciparum succeeds in part because bedridden victims of the disease are more vulnerable to mosquitoes that carry and transmit the parasite. To mitigate malaria, the secret is to improve housing conditions. If people put screens on doors and windows, and use bed nets, it creates an evolutionary incentive for Plasmodium falciparum to become milder and self-limiting. Immobilized people protected by nets and screens can't easily spread the parasite, so evolution would favor forms that let infected people walk around and get bitten by mosquitoes.
There are also a few high-tech tricks for nudging microbes in the right evolutionary direction. One company, called MedImmune, has created a flu vaccine using a modified influenza virus that thrives at 77°F instead of 98.6°F, the normal human body temperature. The vaccine can be sprayed in a person's nose, where the virus survives in the cool nasal passages but not in the hot lungs or elsewhere in the body. The immune system produces antibodies that make the person better prepared for most normal, nasty influenza bugs.
Maybe someday we'll barely notice when we get colonized by disease organisms. We'll have co-opted them. They'll be like in-laws, a little annoying but tolerable. If a friend sees us sniffling, we'll just say, Oh, it's nothing—just a touch of plague.
—Joel Achenbach
Washington Post staff writer
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Drexler, Madeline. Secret Agents: The Menace of Emerging Infections. Joseph Henry Press, 2002.
Grob, Gerald N. The Deadly Truth: A History of Disease in America. Harvard University Press, 2002.
Mims, Cedric. The War Within Us: Everyman's Guide to Infection and Immunity. Academic Press, 2000.
Speildman, Andrew, and Michael D'Antonio. Mosquito: A Natural History of Our Most Persistent and Deadly Foe. Hyperion, 2001.
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