Colds and the Flu - Risk Factors

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Highlights	Complications	Medications
Introduction	Risk Factors	Resources
Diagnosis	Prevention	References

People under Stress

A number of studies suggest that stress increases one's susceptibility to a cold. Stress appears to increase the risk for a cold regardless of lifestyle or other health habits. And once a person catches a cold or flu, stress can make symptoms worse.

It is not clear why these events occur. Some experts believe that stress alters specific immune factors, which cause inflammation in the airways.

Seasonal Incidence

Colds and the flu occur predominantly in the winter. Flu season typically starts in October and lasts into mid March.

The reasons for this seasonal bias are not due to the cold itself, but to other factors. Certainly, the flu and colds are more likely to be transmitted in winter because people spend more time indoors and are exposed to higher concentrations of airborne viruses. Dry winter weather also dries up nasal passages, making them more susceptible to viruses. Some experts theorize that the high rates of viral infections in winter may be due to certain immune factors, which react to light and dark and affect a person's susceptibility to viruses.

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Traveling in Trains, Buses, and Planes

Traveling in close contact with people, whether on trains, planes, or buses, can increase the risk for respiratory infections.

Day Care Centers

Children who attend day care may have an increased risk of colds. However, they may have lower cold rates in their first years of regular school. The colds they catch in day care, then, may bestow some immunity to future colds for a few years. By age 13, such protection has worn off. There is also some evidence that frequent colds in young children may help protect against future allergies and asthma.

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Review Date: 01/29/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).