Asthma affects more than 6 million children in the US.

Asthma (from the Greek άσθμα, ásthma, “panting”) is a common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm1. Symptoms include wheezing, coughing, chest tightness, and shortness of breath. In the United States, asthma affects more than 22 million persons. It is one of the most common chronic diseases of childhood, affecting more than 6 million children in the United States1.

A related condition is wheezing: Whistling noise heard during breathing, when the airways are narrowed as a result of inflammation. Wheezing most commonly occurs on expiration, or breathing out, and is a common sign of worsening asthma. However, wheezing per se is not asthma, and it is not clear that wheezing necessarily progresses to full-blown asthma. Wheezing episodes early in life are a major risk factor for later diagnosis of asthma2. However, the role of viruses in the risk of asthma is still being investigated. The fact that viruses are a risk for asthma exacerbations is on sounder footing. Many other inhaled substances can also exacerbate asthma. 

Page last edited: 17 May 2011


  1. NHLBI Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma. Full Report. National Asthma Education and Prevention Program. 2007 August; (NIH Publication No. 07-4051):
  2. Busse, W. W. Lemanske, R. F., Jr. Gern, J. E. Role of viral respiratory infections in asthma and asthma exacerbations. Lancet. 2010 Sep 4; 376 (9743): 826-34.