The National Institutes of Health recognized World Asthma Day last week. Asthma affects more than 230 million people worldwide, including more than 25 million people in the United States. There is no way to prevent, or to cure, asthma. Existing treatments focus on preventing or controlling disease symptoms, such as wheezing, chest tightness, shortness of breath and coughing. Despite these efforts, each year more than half of children and one-third of adults with asthma in the United States miss school or work because of the disease, approximately 17 million people require medical attention because of an asthma episode, and more than 3,000 asthma-related deaths occur.