The common, contagious cold is a brief, mild illness, usually lasting no more than a week. The flu can last somewhat longer, generally for about one to two weeks. The early symptoms of a cold are headache, sneezing, chills, and/or a sore throat start two to three days after you have been infected.he flu can last somewhat longer, generally for about one to two weeks. The early symptoms of a cold are headache, sneezing, chills, and/or a sore throat start two to three days after you have been infected.