Chronic respiratory diseases


WHO / Marko Kokic

What is asthma?

Asthma is a chronic disease characterized by recurrent attacks of breathlessness and wheezing, which vary in severity and frequency from person to person.

Symptoms may occur several times in a day or week in affected individuals, and for some people become worse during physical activity or at night.

Asthma attack

During an asthma attack, the lining of the bronchial tubes swell, causing the airways to narrow and reducing the flow of air into and out of the lungs. Recurrent asthma symptoms frequently cause sleeplessness, daytime fatigue, reduced activity levels and school and work absenteeism. Asthma has a relatively low fatality rate compared to other chronic diseases.

More information on asthma


  • According to WHO estimates, 235 million people suffer from asthma.
  • Asthma is the most common chronic disease among children.
  • Asthma is not just a public health problem for high income countries: it occurs in all countries regardless of level of development. Over 80% of asthma deaths occurs in low and lower-middle income countries.
  • Asthma is under-diagnosed and under-treated, creating a substantial burden to individuals and families and possibly restricting individuals’ activities for a lifetime.


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