The common cold, also known as acute nasopharyngitis, was a viral Human illness of the upper respiratory system that had existed at least since Earth's Stone Age. The primary symptoms of the illness included a sore throat, coughing, and either a stuffed or runny nose. The virus was contagious, and could be spread by both direct contact and droplet infection.
In 2151, Malcolm Reed exclaimed that Humans could travel past light speed, yet still could not cure the common cold. Phlox replied that there was no cure or treatment for the illness except for methods similar to those used in the 20th century. (ENT: "Sleeping Dogs") Jonathan Archer once stated that "if the Vulcans had their way they'd blame micro-singularities for the common cold." (ENT: "Shuttlepod One")
Dr. McCoy noted that modern medicine was still searching for a cure for the common cold in the 23rd century. (TOS: "Plato's Stepchildren") McCoy found a number of promising biological candidates on Omega IV that might lead to a viable cure. (TOS: "The Omega Glory") Scotty also mentioned that the common cold was yet uncured. (TOS: "The Lights of Zetar")
Tom Paris once told The Doctor that when he was nine years old, he had a cold. His childhood doctor, Dr. Brown who still made house calls, "whipped up a pot of garlic soup and brought it over himself." (VOY: "Cathexis")