Heavy Precipitation Linked to Disease Outbreaks

August 15, 2001

Especially during hurricane season, it's worth noting that a heavy rainstorm can do far worse than dampen your mood. In the first nationwide study of its kind, Johns Hopkins researchers announced on Jul. 31, 2001 that 68% of waterborne disease outbreaks reported over a 47-year period were preceded by precipitation events in the top 20% of volume for the affected watershed. Reported outbreaks (which may be only about 10% of actual outbreaks) occurred throughout the US.

  • Johns Hopkins Bloomberg School of Public Health: Frank Curriero, 410-614-5817. For a faxed copy of the study (published in the August 2001 American Journal of Public Health), Johns Hopkins media: Ming Tai, 410-955-6878.
When storms produce more flow than storm sewers can handle, sewage systems often discharge untreated sewage directly into lakes, streams, and estuaries -- especially when storm and sanitary sewers are combined. A major portion of waterborne disease comes from people drinking water contaminated with germs or parasites from human or animal feces. Storms also wash fecal material into water bodies directly from farm land and city streets. (See Centers for Disease Control and Prevention MMWR December 11, 1998 / 47(SS-5);1-34 Surveillance of Waterborne Disease Outbreaks -- United States, 1995-1996. Click on tables, esp. table 2.) In many outbreaks, however, the specific disease-causing germs and their ultimate source may never be identified. EPA is still evaluating a proposed rule on sanitary sewer overflows that was issued during the last days of the Clinton Admin.: KevinWeiss, 202-564-0742.

The new research could paint a gloomier picture of global climate change, which some researchers predict will increase the number of heavy-precipitation events. US Natl. Assessment of the Potential Consequences of Climate Variability and Change, health sector.

Along with bacteria and viruses, antibiotic-resistant organisms are spreading through watersheds. See TipSheet, June 20, 2001.

  • The NJ Dept. of Environmental Protection has found that increased rainfall consistently leads to significant increases in potentially harmful organisms such as Giardia and Cryptosporidium. Tom Atherholt: 609-984-2212.
  • The Natl. Water Research Inst. is conducting studies on waterborne disease, examining urban factors such as residential irrigation, feral and domestic animals, and impervious pavement. Ronald Linsky: 714-378-3278.


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