Neil W. Johnston, MSC, of St. Joseph's Healthcare
and McMaster University, Hamilton, Ontario, Canada and colleagues
were head researchers on the project and looked to determine the
sequence of timing for September asthma hospitalization epidemics
in children and adults, and determine whether school-age children
transmit the viral infections that often lead to asthma attacks
Researchers used Canadian hospital admission data
from 1990 to 2002 for the study. Study participants were divided
into three age groups: preschool children ages 2 to 4; school-age
children 5 to 15 years old; and adults 16 to 49 years old. The researchers
also divided Canada into four geographic ranges based on latitude.
Some of the findings include the following:
- On average, the epidemic peak for school-age children
was 17.7 days after Labor Day (the day after the holiday is traditionally
the beginning of the school year), 19.4 days after Labor Day for
preschool children and 24 days after Labor Day for adults.
- Timing of the asthma exacerbation peak from north
to south was also consistent with differences in weather conditions
and in-school allergen levels.
- The sequence of the epidemic remained consistent,
suggesting the viral infections were transferred from the school-age
children to the preschool children and adults with whom they were
- School-age children were the starting point for
the viruses, with children ages 5 to 7 the leading group affected
by the asthma epidemic. Researchers suggest this could be because
they are not as resistant to the infections and because infections
transmit easily from children to other children or adults because
of children's social behavior.
- Rhinovirus infections are the leading cause of
respiratory infections for children in the early fall. Between 80
to 85 percent of children with wheezing episodes test positive;
half the adults with a wheezing episode also have rhinovirus infections.
Johnston and colleagues concluded that finding ways
to prevent respiratory infections in children is a key component
to lessening the annual asthma outbreak for all ages.
The research report, The September epidemic of asthma
hospitalization: School children as disease vectors, was published
in the March 2006 issue of the Journal of Allergy and Clinical Immunology
(JACI), a peer-reviewed, scientific journal of the American Academy
of Allergy, Asthma and Immunology.