According to Dr. John Spencer Chikeziem Archinihu, MD Both are very serious infections and also viral infections. Cold and flu effect the respiratory system. It is difficult to explain both apart because of both affect throat, nose, and Lungs. But the difference is that it is common to get a cold more than twice in a year, In another case, people get the flu only a few times in 10 years. FLu is worst than cold.