The flu is caused by a set of viruses which occur in epidemics during the winter.
Symptoms are similar to a cold, but tend to be more severe.
A flu usually has a sudden onset and lasts 1-2 weeks. Complications are uncommon in young, healthy people but may include pneumonia, bronchitis, ear or sinus infections. Consider getting a flu shot. A cold is an upper respiratory infection caused by a virus. Symptoms of a cold usually include a runny nose, sneezing, coughing, sore throat, muscle aches, headaches, low grade fever and congestion of the ears, nose and head.