Acute bronchitis is a contagious viral infection that causes inflammation of the bronchial tubes, which are the airways that carry air into your lungs. It is usually caused by the same viruses that cause colds and the flu, but it can also be caused by bacterial infections or exposure to irritants such as smoke, dust, or fumes. The inflammation causes increased mucus production and other changes, leading to symptoms such as coughing (with or without mucus), soreness in the chest, feeling tired, mild headache, mild body aches, sore throat, and shortness of breath. Acute bronchitis can last less than three weeks and usually gets better on its own without antibiotics. However, it can be serious in people with lung or heart diseases, and pneumonia is a complication that can follow bronchitis. To feel better while your body fights off acute bronchitis, you can get plenty of rest, drink plenty of fluids, use a clean humidifier or cool mist vaporizer, use saline nasal spray or drops to relieve a stuffy nose, and ask your doctor or pharmacist about the right dosage of over-the-counter medicines for your age.