Common cold
From Memory Alpha, the free Star Trek reference.
The common cold, also known as acute nasopharyngitis, is a viral Human illness that has existed at least since Earth's Stone Age. The primary symptoms of the illness include a sore throat, coughing, and either a stuffed or runny nose. The illness is contagious; the virus is 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")
By the mid-24th century, the common cold was apparently cured, though earlier in the century it still existed. (TNG: "The Battle", "Datalore", "Ensign Ro")
On stardate 44723.5 Geordi La Forge experienced headaches, caused by the common cold. (TNG: "Cause and Effect")
