If a cold is misdiagnosed as flu, there's no problem. At worst, a cold can occasionally lead to secondary bacterial infections of the middle ear or sinuses, which can be treated with antibiotics. But if the flu is misdiagnosed as a bad cold, potentially life-threatening flu complications like pneumonia may be overlooked. Some of the symptoms of a cold and flu are similar, but the two diseases can usually be distinguished. The first symptoms are usually a scratchy, sore throat, followed by sneezing and a runny nose.
Temperature is usually normal or only slightly elevated.
A mild cough can develop several days later. Cold symptoms usually last from two days to a week. Signs of the flu include sudden onset with a headache, dry cough, and chills. The symptoms quickly become more severe than those of a cold. The fever typically begins to subside on the second or third day, and then respiratory symptoms like nasal congestion and sore throat appear.