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This article orginally appeared in the Jan. 14, 2009 issue of the St. Louis Post Dispatch.

Asthma is becoming more common in developed countries, but no one knows exactly why. Researchers are sure of one thing, though: A child is most likely to develop asthma if there is a family history of allergies and asthma.

A new study published in the December American Journal of Respiratory and Critical Care Medicine suggests that children also might be at increased risk of getting this common chronic disease of the lungs because of something else that parents don't have much control over — kids' birthdays.

Looking at more than 95,000 infants born from 1995 to 2000, researchers followed the children through 2005. What they found: Those born in the autumn were nearly 30% more likely to get asthma. The researchers say it's because babies born in the fall months are much more likely to get common wintertime viral infections like respiratory syncytial virus (RSV), a major cause of respiratory illness in young children.

So, what does that have to do with asthma?  Children who've had RSV or bronchiolitis (which is usually caused by a viral infection, most commonly RSV) may be more likely to develop asthma later in life.  Still undetermined is whether these illnesses actually cause asthma or whether children who eventually develop asthma were simply more prone to developing those sicknesses as infants anyway. Research continues into the relationship between RSV, bronchiolitis, and the later development of asthma.

In the meantime, though, the researchers in this latest study say preventing infections with common winter viruses in babies could help prevent asthma, too.

What This Means to You

Asthma can be tough to diagnose in children younger then 5 years, especially in infants, because other conditions have similar symptoms.

Bronchiolitis, in particular, often mimics asthma in babies. The infection affects the tiny airways (called bronchioles), causing them to become narrowed, which makes breathing more difficult. Infants are often affected because their airways are so small that they become blocked more easily than those of older children or adults. Symptoms of bronchiolitis include a runny nose,  rapid breathing, a cough, wheezing, and fever

For children with asthma, viral infections (like RSV, bronchiolitis, and the common cold or flu) can trigger asthma symptoms or make them worse. Kids may react to triggers (like viruses, animal dander, dust, mold, and pollen) over time, with gradual exposure, or suddenly and without warning. The result is usually an asthma flare-up (or attack) — when the lungs' already-inflamed airways become more swollen and clogged with sticky mucus, and the muscles around the airways tighten, leaving little room for air to flow through.

“If a baby is wheezing, it can sometimes just be a one-time, temporary viral infection,” explains Dr. Bradley Becker, co-director of the Asthma Center for Children at SSM Cardinal Glennon Children’s Medical Center, and an associate professor of pediatrics at Saint Louis University School of Medicine.  “If your baby is wheezing, coughing, short of breath, it’s best to be safe and consult your child’s physician.”

Whether your child has asthma or not, it's always wise to try to keep infectious bugs at bay. To keep them from invading your household:

  • Try to steer clear of crowded places (like shopping malls) and anyone with a cough, cold, or the flu if you have an infant, especially during cold and flu season,.
  • Make sure everyone who comes in contact with your baby washes their hands well and often.
  • Teach young children how to wash their hands properly every time (and make sure you do the same):
    • Use warm water and soap and lather up for about 10 to 15 seconds.
    • Get in between the fingers and under the nails where uninvited germs like to hang out. And don't forget the wrists!
    • Rinse, then dry well with a clean towel. 

The few seconds you all spend at the sink every day could save you some trips to the doctor's office.

Dr. Bob Wilmott is Chief of Pediatrics at SSM Cardinal Glennon Children’s Medical Center and is a Professor of Pediatric Medicine at Saint Louis University School of Medicine. If you have a question about your child’s health, go to the “Ask Dr. Bob” section of the Cardinal Glennon Web site at


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