The Why Files The Why Files -- whyfiles.org

Infection dissection
POSTED 1 NOV 2000

I mutate. You mutate. They mutate.
"It's a war out there." That's what they used to say on "NYPD Blue," anyway, to prepare the cops for their daily battle against devious, well-armed criminals. Like the bad guys on fictional TV, microbes are potent adversaries. But we'd rather see the struggle against infectious disease not as a law-and-order morality play, but rather as an evolutionary drama, a constant battle for biological supremacy.

Masks, gowns and sterile cloths prevent microbes from spreading during surgery.

That's the approach used by Joshua Lederberg, formerly of Rockefeller University, who's a guru of the emerging disease biz. "Here we are; here around the bugs," he wrote. "They are looking for food; we are their meat in one sense or another. How do we compete with them? There are so many of them, they reproduce so much more quickly than we do..." (see "Epidemic!" in the bibliography)

Protective clothing such as masks, gowns and gloves prevent pathogens from passing between doctors and patients during bypass surgery. Exposure to blood kills many medical workers during the early stage of Ebola outbreaks. University of Wisconsin-Madison Medical School, Edward Joseph, photographer.

What makes microbes menacing?
The dangerous traits of pathogens seem like a hybrid of the seven deadly sins and the seven heavenly virtues.

Charity. Bacteria help each other by sharing bits of DNA that help them resist antibiotics.

Sloth. When higher organisms copy DNA, they make a big effort to get it right. Many pathogens don't bother, since slothful copies lead to mutations. Mutations may kill the new pathogens -- or make them more deadly or increase their ability to outwit the immune system or defeat antibiotics.

Gluttony. Bacteria number in the gezillions, and they need a lot of food (translated: you and me).

Fortitude. Maybe we should say "fleetness," but at any rate, pathogens do not believe in "haste makes waste." Bacteria, for example, can double in number in 20 minutes.

Indifference. From an evolutionary point of view, 99.999 percent of new pathogens can die -- if the remainder survive and find a new victim to infect. We humans, of course, would be horrified by a 1 percent mortality rate.

Anger. Some of the worst pathogens attack the immune system, disabling the body's defenses. HIV/AIDS is the classic example of the preemptive strike. What we got? What do humans have to counter this formidable onslaught? We have smarts, and we have biological defenses.

Smarts. We can invent new medicines. We can devise vaccines that prime the immune system for new pathogens. We can reduce the social, political, economic and ecological conditions that promote new infectious diseases (more on this shortly). We can pay the Centers for Disease Control and Prevention to monitor and control new outbreaks. The immune system. Too complicated to describe here, the various branches of the immune system are constantly mutating on their own right, looking for new foreign proteins to attack.

And the winner is...
Infectious disease involves a paradox: A pathogen that kills its host before it infects something else may be a microbial dodo. Since a sufferer who's walking around is usually more infectious than a corpse, pathogens tend to evolve into less deadly forms.

That's the good news.

The bad news is that new diseases with near-absolute death rates are constantly emerging. HIV and Ebola both came from tropical Africa.

Could this reflect ecological change and population pressures?

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