SCIENCE: Should Science Pull the Trigger on Antiviral Drugs—That Can Blast the Common Cold? It’s not as open-and-shut as you might think.

Our bodies are rife not just with bacteria but with viruses too. Even when we’re perfectly healthy, we have trillions of viruses inside of us. Scientists are only beginning to survey this viral ecology, but some suspect that it may actually be essential to our health. Many animals depend on viruses. Aphids, for example, need a virus that makes a toxin that prevents wasps from laying eggs inside their bodies. Scientists have found that infecting mice with lymphotrophic viruses protects them from developing diabetes. Other viruses attack cancer cells.

We may have such beneficial viruses inside our own bodies as well, waiting to be discovered. These viruses may not even infect our own cells but could instead be inside the bacteria that colonize us. Some species might keep the populations of their microbial hosts in check, like predators thinning a herd. Some viruses merge with bacteria rather than killing them, providing their hosts with useful genes for feeding or fighting off competitors. All of these microbe-infecting viruses may ultimately help us stay healthy.

It’s conceivable that a broad-spectrum antiviral could devastate this complex, poorly understood biological jungle. As beneficial viruses disappeared, we might pay the price, developing diseases that the viruses used to keep at bay. Even Lingappa concedes that virus-killing could potentially go too far. “I don’t think we want to kill all viruses,” he says. “You only know about a virus when it does something bad. We’ve evolved with them. There’s probably some virus out there doing something good.”

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