Oct 22, 2004 (CIDRAP News) The United States had fewer reported disease outbreaks linked to drinking water in 2001 and 2002 than in the preceding 2 years, and they affected about half as many people, according to the Centers for Disease Control and Prevention (CDC).
An estimated 1,020 people got sick from drinking contaminated water in 31 outbreaks in 2001 and 2002, the CDC reports today in a supplement to Morbidity and Mortality Weekly Report. That compares with 39 outbreaks and an estimated 2,068 illness cases in 1999 and 2000.
However, outbreaks in the more recent period caused seven deaths, versus only two deaths in 1999-2000, the report says.
Five norovirus outbreaks accounted for close to three-fourths of all the illness cases727 of 1,020, the report says. Five outbreaks were blamed on parasites, five on chemical contamination, six on Legionella species, and three on other bacterial pathogens. The causes of seven outbreaks were never identified, but all were thought to be infectious agents.
In the previous 2-year period, causes went unidentified in 17, or 44%, of the outbreaks, the report says. The reduction in unexplained outbreaks in 2001 and 2002 probably reflects both improved outbreak investigations and better diagnostic capabilities, the CDC says.
The six Legionella outbreaks involved 80 cases with 41 hospitalizations and four deaths. All the outbreaks were in large buildings or institutions and were related to growth of Legionella species in the water distribution systems, the CDC says.
Two of the seven deaths were caused by the parasite Naegleria fowleri, in the first such outbreak linked to a drinking water system in the United States. The outbreak occurred in Arizona in October 2002.
Of the 31 outbreaks, 23 involved groundwater sources, and 10 of these involved untreated groundwater. Two outbreaks involved treated water from rivers and streams. The report does not identify the water sources for the six outbreaks involving Legionella.
CDC. Surveillance for waterborne-disease outbreaks associated with drinking waterUnited States, 2001-2002. MMWR 2004 Oct 22;53(SS08):23-45 (Full text)
CDC. Surveillance for waterborne disease outbreaksUnited States, 1999-2000. MMWR 2002 Nov 22;51(SS08):1-28 (Full text)