Virologists at Duke University Medical Center have discovered that, under the right conditions, a common cold virus closely related to poliovirus can cause polio in mice. The researchers injected a cold virus called Coxsackievirus A21 into mice that were engineered to be susceptible to this particular virus. However, instead of developing a cold, the mice unexpectedly displayed paralytic symptoms characteristic of polio. The researchers determined that administering the virus directly into muscles, instead of the virus’s normal home in the nasal cavity, was critical for development of polio. The findings challenge traditional views as to what defines a poliovirus, said Matthias Gromeier, M.D., a Duke virologist and senior author of the study.