Disease in the Age of Evolutionary Medicine

Alexander Bivelich first came to the Tomsk Prison in central Russia in 1993. Convicted of theft, he was sentenced to three years. Two years into his term he began to cough up phlegm, and he spiked a fever. The prison doctors discovered a small infection in his left lung and diagnosed him with tuberculosis, a disease caused by the bacteria Mycobacterium tuberculosis. Bivelich might have picked it up by inhaling a droplet of sputum that had been hacked up by an infected prisoner, the bacteria settling into his own lungs. “I never thought I’d be infected,” says Bivelich. “At first I did not believe what the doctors told me.” But as the disease took hold in his body, he came to believe.

Tuberculosis ought to be an easily treated disease. It has been almost 60 years since Selman Waksmann of Rutgers University discovered that bacteria produce proteins that can kill Mycobacterium. Waksmann’s drug joined a growing group of bacteria‑killing antibiotics being discovered at the time. They were so lethal to bacteria that medical researchers thought infectious diseases such as tuberculosis would be eradicated within a few decades.

But Mycobacterium did not surrender Bivelich so easily. Prison doctors were able to treat him with antibiotics for a few months until he was released from jail in 1996. In 1998 Bivelich was back at Tomsk Prison, arrested for another theft. He had gotten no treatment for his TB on the outside, and when the prison doctors took another x‑ray of his lungs, they found that the infection had spread during his freedom. Now his left lung was ravaged by lesions along with the right. They began giving him antibiotics again, but before long their tests revealed that the drugs were not stopping the spread of the bacteria. What were once wonder drugs were, for Bivelich, useless.

The prison doctors decided to switch Bivelich to a new regimen of antibiotics–powerful, expensive drugs hard to come by in Russia–and for a few months they managed to stabilize his health. But in time even these drugs proved useless. By July 2000, Bivelich’s doctors were contemplating cutting out the diseased parts of his lungs. If the surgery and the drugs didn’t stop the tuberculosis soon, he would probably die.

Bivelich’s fate is not unusual in Russia. Drug‑resistant strains of tuberculosis have emerged in Russia’s crowded, filthy prisons, and today 100,000 prisoners carry strains of TB resistant to at least one antibiotic. Like Bivelich, many of these prisoners are petty criminals serving short terms. But thanks to tuberculosis, those short terms can become death sentences.

Bivelich is the victim of coevolution’s dark side: the frightening speed at which parasites adapt to their hosts. Just as orchids adapt to bees, or fruit trees to the animals that spread their seeds, pathogens are forever evolving into new forms, hitting upon new ways to overrun their hosts’ defenses. And just as many pesticides have lost their power to stop killing insects, drugs are becoming impotent in the face of mutating parasites. Drug‑resistant forms of tuberculosis and other diseases are now evolving around the world, killing thousands. In the future, they have the potential to kill millions.

By understanding evolution, medical researchers may be able to find new ways to fight diseases. In some cases, by uncovering the evolutionary history of a disease–how a parasite first made humans its host and how humans evolved in response–they may find a cure. In other cases, scientists may even be able to harness the power of coevolution to tame the agents of disease.