Common cold is a common disease of Earth. Colds are caused by viruses, affecting the upper respiratory tract. Common symptoms of the common cold are stuffy nose, sneezing, coughing and fatigue. The cold is spread through the air when you sneeze.
In 1997, Apophis placed two viruses in two hollow teeth that he had placed in Rya'c so he could wipe out the Tau'ri. Drey'auc told Teal'c that Rya'c had lost two teeth in training with Bra'tac. Dr. Janet Fraiser examined teeth and discovered they had something in them. After Fraiser had discovered the virus in the teeth and destroyed them, she informed Major General George S. Hammond and SG-1. Major Samantha Carter and Fraiser said if the virus had met each other, they would let loose a dangerous virus which would kill all life on Earth in a few weeks. Colonel Jack O'Neill thought it sounded like Anthrax. According to Fraiser as anthrax would be like a common cold in comparison with the virus. (SG1: "Family")