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INFLUENZA

If there’s one word school principals dread hearing Tiny influenza particles,
each winter, it’s “influenza.”
emitted by talking and
In the past two years, schools in at least a dozen U.S. breathing, are infectious as
states shut down because of flu outbreaks. 34 well. These particles can travel

“Flu is a major contributor to absenteeism,” said across a room and hover
Wisconsin epidemiologist Huong McLean, Ph.D., for hours.
lead author of a CDC-funded study on school
absences and influenza. 35 Handwashing is critical for containing the spread
of influenza, and many schools diligently train
That’s because the flu is so easily spread. teachers and students before flu season. However,
compliance is notoriously low. In surveys, even 67%
Imagine a sunny classroom window where you of adults admit they’ve bypassed the soap in public
can see dust floating in the air. “That’s where your bathrooms. At hospitals, 76% of doctors and
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influenza particles sit,” explains Dr. Bischoff of Wake nurses fail to comply with handwashing protocol,
Forest School of Medicine. and according to Swiss researchers, the hands of
doctors and nurses deposit potentially harmful
Large influenza particles, emitted by a cough or a microbes every 4 seconds onto patients and hospital
sneeze, are the most potent. Once released into surfaces. 38,39 First-graders are not likely doing any
the air, these particles — 50 to 100 microns in size, better.
about the diameter of a human air — travel 3 to 6
feet before dropping onto surfaces.

Large influenza particles,

emitted by a cough or
a sneeze, are the most potent.

But tiny influenza particles, emitted by talking and
breathing, are infectious as well, Bischoff’s research
shows. These particles — as small as 1 to 2 microns
(a micron is a millionth of a meter) — can travel
across a room and hover for hours. Up to 89%
of flu-carrying particles are of the small, nomadic
variety. 36

Even if all flu-infected students sneezed into tissues
and covered their mouths to cough, a highly unlikely
scenario, the virus would still wander freely around
school. Schools also work hard to promote the flu vaccine,
yet vaccination rates in the United States hover
What’s more, people infected with the virus are just below 60% for children. Even in a good year,
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contagious for about four days before they develop vaccines reduce the risk of contracting the flu by only
symptoms. So seemingly healthy students have 40% to 60%. In pandemic years, the vaccine misses
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ample opportunity to propel the virus into the air the mark badly, with effectiveness below 20%.
or deposit infectious particles on doorknobs, desks,
books, or friends.

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