The CDC says there are millions of cases of the common cold that affect both adults and children in the US each year. Adults come down with roughly two or three colds annually and while they tend to last around a week, there's no cure. But according to Business Insider, there are ways to make yourself more comfortable as your immune system fights off the virus. Dr. Aimee Desrosiers is an infectious disease expert. She says the number one immune-system booster is rest, plain and simple.