Respiratory tract infection (RTI) is defined as any infectious disease of the upper or lower respiratory tract. Upper respiratory tract infections (URTIs) include the common cold, laryngitis, pharyngitis/tonsillitis, acute rhinitis, acute rhinosinusitis and acute otitis media. Acute respiratory infection is a serious infection that prevents normal breathing function. It usually begins as a viral infection in the nose, trachea (windpipe), or lungs. Also, acute respiratory infections are infectious, which means they can spread from one person to another. A majority of upper respiratory infections are due to self-limited viral infections. Occasionally, bacterial infections may cause upper respiratory infections. Most often, upper respiratory infection is contagious and can spread from person to person by inhaling respiratory droplets from coughing or sneezing. Respiratory symptoms are common symptoms of lung or heart conditions, emotions, or injury. The medical terms for respiratory symptoms include dyspnea (difficulty breathing), tachypnea (rapid breathing), hypopnea (shallow breathing), hyperpnea (deep breathing), and apnea (absence of breathing).