The common cold is an incurable, nonlethal respiratory virus which attacks humans. Its symptoms include sneezing, coughing, congestion, and fever, and typically affect the sufferer for a period of a week or two.
Common Cold in Earthgrip
The common cold virus was engineered by the ancient Foitani Great Ones before the Suicide Wars. A Foitan expedition had visited Earth, and one of their researchers was killed by primitive humans. (The expedition nevertheless managed to abduct a male and female specimen.) The Foitani decided that humans were too violent and erratic to be allowed to develop into an advanced space-faring civilization, and so, per standard Foitan operating procedures, a respiratory virus was engineered which was supposed to be lethal, communicable, and incurable, and was introduced into the human population. The virus was indeed communicable and incurable but did not prove to be lethal, and it eventually came to be known as the common cold.
The Foitani did not revisit Earth before the Suicide Wars, when their empire was destroyed and their few surviving colonies plunged into dark ages. Nearly 30,000 years later, spacefaring humans ranged as far as the Great Ones had at their height. The truth about the common cold (as well as other matters) was discovered by the crew of the Harold Meeker, a human civilian starship whose personnel had been commandeered for an expedition into a mysterious fortress with a genetic anti-Foitani safeguard. When modern Foitani learned knew of their species' creation of the virus, they were sometimes perplexed and even a little offended that humans were not extinct.