Interactions among viruses can help them succeed inside their hosts or impart vulnerabilities that make them easier to treat. Scientists are learning the ways viruses mingle inside the cells they infect, as well as the consequences of their socializing. Although it is debatable whether viruses are living things, they do compete, cooperate and share genome materials that can sometimes alter their responses to antiviral drugs, result in new variants or play a role in virus evolution. A paper today in Nature Ecology & Evolution by UW Medicine scientists looks at the evolution of poliovirus resistance to a promising experimental antiviral drug, pocapavir. While it seemed counterintuitive, the researchers demonstrated that lowering the potency of pocapavir could improve the situation by enhancing the survival of enough susceptible viruses to continue sensitizing the resistant ones.