We've heard of flu season, but wheeze season? That's right, as children head back to school in September, rates of asthma episodes quadruple, peaking about 17 days after Labor Day.

Hospitalizations this time of year are so frequent that the phenomenon has been dubbed the September Asthma Epidemic. And it's affecting more people than ever because the prevalence of asthma has increased at least threefold during the past several decades, with the sharpest increase among children under the age of five.

Why is this happening -- and what can be done to prevent attacks?

• Waiting to exhale: Doctors aren't certain why the September flare-up happens, but most think it has to do with the sudden interaction students have with large groups of other children, increasing their chances for catching a virus; one Canadian study found that during September, 60 percent of all children who went to the ER for asthma also had viral infections (mostly colds).

Children with allergies -- the most common trigger for asthma -- catch 50 percent more viruses than those without allergies. Adding to the problem: Many parents reduce their children's asthma-controlling medication in the summer, when asthma rates are low, but they don't re-start the medications before school starts.

• Why so many? About 24.7 million people in the United States have been diagnosed with asthma; at least 7.7 million of them are under the age of 18, according to the Centers for Disease Control & Prevention.

Asthma is the leading serious, chronic illness among American children. Asthma rates in those under the age of 5 have increased more than 160 percent from 1980 to 1994, reports the American Academy of Allergy, Asthma, & Immunology.

Research has led to a number of possible explanations -- an increase in air pollutants, rising obesity rates, more sedentary lifestyles, exposure to second-hand smoke -- but there is no agreement on the reasons. A Norwegian study last year found that babies born by Caesarean section have a 50 percent increased risk of developing asthma, compared to babies born naturally.

• Triggers: For asthmatics, staying away from triggers that cause mucous membranes to become inflamed is the key to being attack-free. Triggers can include pollens, pet dander, cold air, certain chemicals, dust mites, plants and even thunderstorms, according to one Georgia study.

• Treatments: The good news is today's therapies are much more effective than those of 30 years ago, so the number of severe complications from asthma is actually decreasing.

Inhaled corticosteroids taken over months at a time are considered the most effective for long-term control, says the American Academy of Allergy, Asthma & Immunology. Inhaled rescue drugs, such as Ventolin, relax the muscle spasm around an irritated airway immediately, but should not be used on a daily basis.

Other ways to reduce the risk of attacks include washing bed linens in hot water at least once a week, using allergen-prevention pillowcases and mattress covers, and reducing exposure to cigarette smoke. Research shows that swimming also helps reduce asthma symptoms in children.

• More info: National Heart, Lung and Blood Institute, www.nhlbi.nih.gov/health/dci/Diseases/ Asthma/Asthma_WhatIs.html.

Get Smart appears every other week, and offers a quick overview of health and medical topics in the news. Got a question or suggested topic? E-mail jmailander@MiamiHerald.com.

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