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What Is This Indicator, and Why Is It Important?
This indicator reports the number of disease outbreaks—which
generally means at least two people getting sick—attributed
to drinking water that is untreated or where treatment has
failed to remove disease-causing organisms, or to swimming
or other recreational contact at lakes, streams, and rivers
(see coastal recreational
water quality).
Ensuring that water is fit to drink and swim in without fear
of disease is a basic societal objective. The number of disease
outbreaks that can be attributed to contaminated water is
a direct measure of the fitness of the nation’s waters
for these two key uses.
What Do the Data Show? The number of disease
outbreaks attributable to contaminated drinking water declined
significantly overall from 1973 to 2002. Since 1986, the
average number of outbreaks per year was lower than the average
during the 1973–1985 period, although there was notable
year-to-year variation. There is also notable variation
in the number of outbreaks associated with recreational
contact, which have increased significantly since 1978.
Since 1990, the number of outbreaks associated with drinking
water and the number associated with recreational contact
have followed a similar pattern.
Discussion This indicator reports outbreaks,
not the number of people who become ill. Thus, depending on
the location of contamination problems, the size and type
of water delivery system, and other factors not related to
environmental quality, the trend in the number of people affected
may be different from the trend in the number of outbreaks.
Doctors and state and local public health officials report
data on outbreaks to the Centers for Disease Control and Prevention.
Whether an outbreak is identified and reported depends on
many factors, so these reports are best considered an indication—rather
than a perfect record—of the true incidence of waterborne
disease outbreaks.
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