An Uncommon Cause for the Common Cold Scientists at UW-Madison have constructed a highly detailed three-dimensional model of the recently discovered rhinovirus C, which shows why there’s no remedy for an all-too-prevalent virus. Called the “missing link” cold virus, rhinovirus C is believed to be responsible for up to half of all childhood colds; together with rhinoviruses A and B, it is causes millions of illnesses a year. All three cold virus strains contribute to the common cold. Since antiviral drugs work by attaching to and modifying surface features of the virus, a drug must fit the structure of the virus in order to be effective. The protein shell of rhinovirus C is distinct from other strains of cold viruses, which is why previous drug trials have failed. Treatments that work well against the A and B strains of cold virus were built to take advantage of specific surface features, but the surface features that let rhinovirus C dock with host cells and evade the immune system are different from those of rhinovirus A and B. Rhinovirus C was not discovered until 2006, when advanced gene sequencing revealed the virus had been lurking in human cells alongside the more observable A and B virus strains. Based on C’s distinct surface structure, UW-Madison virologists predict that a C-specific drug will be required. Thanks to the new cold virus model, which was based on the genetic sequences of 500 rhinovirus C genomes, researchers have a fighting chance of finally curing the common cold.