The very young and the very old are at higher risk for upper respiratory tract infections and their associated complications.
Children. Young children are prone to colds and may have as many as 12 colds every year. Millions of cases of influenza develop in American children and adolescents each year.
Before the immune system matures, all infants are susceptible to upper respiratory infections, with a possible frequency of one cold every 1 - 2 months. Smaller nasal and sinus passages also make younger children more vulnerable to colds than older children and adults. Upper respiratory infections gradually diminish as children grow, until at school age their rate of such infections is about the same as an adult's. There is almost never cause for concern when a child has frequent colds, unless the colds become unusually severe or more frequent than usual.
The Elderly. The elderly have diminished cough and gag reflexes, and their immune systems are often weaker. They are therefore at greater risk for serious respiratory infections than the young and middle-aged adults.
Exposure to Smoke and Environmental Pollutants
The risk of respiratory infections is increased by exposure to cigarette smoke, which can injure airways and damage the cilia (tiny hair-like structures that help keep the airways clear). Toxic fumes, industrial smoke, and other air pollutants are also risk factors. Parental smoking increases the risk of respiratory infections in their children.
People with AIDS and other medical conditions that damage the immune system are extremely susceptible to serious infections.
Cancers, especially leukemia and Hodgkin's disease, put patients at risk. Patients who are on corticosteroid (steroid) treatments, chemotherapy, or other medications that suppress the immune system are also prone to infection.
People with diabetes are at a higher risk for the flu.
Review Date: 01/29/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.