By John Brennan
Updated Aug 30, 2022
Every year, the United States records over a billion cases of the common cold. While the name implies a single illness, it is actually a collection of more than 200 distinct viruses that share a common infection site—typically the nose and throat. Each virus has its own evolutionary story.
Viruses hijack host cells to replicate, but the replication process is error‑prone. These errors introduce mutations, creating genetic diversity within a viral population. When multiple strains infect the same cell, recombination can occur, further shuffling genetic material. Both rhinoviruses and coronaviruses exhibit high mutation rates, enabling rapid emergence of new strains.
In 2009, researchers at the J. Craig Venter Institute and the University of Wisconsin released complete genomes for all 99 human rhinovirus strains. Analysis of this data revealed a previously unrecognized species—HRV‑D—while showing that HRV‑A and HRV‑C share a closer ancestry and are closely related to HRV‑B. Rhinoviruses are genetically nearest to human enteroviruses, which primarily infect the gastrointestinal tract. Current evidence suggests a common ancestor between rhinoviruses and enteroviruses, though the exact timing of divergence remains unclear.
A 2008 study published in the Journal of Virology compared human and avian metapneumoviruses and found a strong genetic link. The data imply that the avian strain crossed over into humans approximately 200 years ago, becoming the human metapneumovirus responsible for cold symptoms.
Research into coronavirus evolution has been propelled by the 2003 SARS outbreak. A 2007 study in the Journal of Virology indicates that modern coronavirus lineages likely originated from a common ancestor infecting bats, before spilling over into other species—including humans. This zoonotic pathway explains the diversity of coronaviruses that contribute to the common cold.
