rhinovirus

One of a group of small RNA-containing viruses responsible for about 40% of common colds. They consist of an icosahedral (20-sided) protein shell, about 20nm (20 × 10−9m) in diameter, surrounding genetic material in the form of a single strand of RNA. They infect and reproduce in the cells lining the nose and throat, but it is the white blood cells' response to their presence that is responsible for cold symptoms. There are more than a hundred strains, or serotypes, of rhinovirus and infection by one strain does not confer immunity from infection by any of the others.

The outer shell of a rhinovirus is pitted with depressions, called ‘canyons’, which fit onto specific protein receptors on the surface of nasal epithelial cells. Once attached, the virus enters the cell and releases its genetic material into the cytoplasm, where it makes use of the cell's resources to produce thousands of copies of itself. The cell breaks up to release the viruses, which then infect neighbouring cells or are expelled from the nose in mucus droplets to infect another individual.

Rhinoviruses belong to the Picornaviridae family of viruses, which also includes the polio and foot-and-mouth disease viruses.