CDC Releases Surveillance Data on Waterborne Disease Outbreaks

In 2007-2008, the most recent year for which waterborne disease outbreak data are finalized, 134 outbreaks were associated with recreational water and 36 outbreaks were associated with drinking water.

CDC has released two MMWR Surveillance Summaries: “Surveillance for Waterborne Disease Outbreaks and Other Health Events Associated with Recreational Water—United States, 2007-2008” and “Surveillance for Waterborne Disease Outbreaks Associated with Drinking Water—United States, 2007-2008.”

The reports cover outbreaks associated with recreational water (e.g., swimming pools) and drinking water. In 2007-2008, the most recent year for which waterborne disease outbreak data are finalized, 134 outbreaks were associated with recreational water and 36 outbreaks were associated with drinking water.

From January 2007-December 2008, 134 recreational water illness outbreaks were reported by 38 states and Puerto Rico, with at least 13,966 cases of illness. This represents the highest number of recreational water illness outbreaks ever reported in a two-year span. The number of recreational water illness outbreaks increased by 72 percent since 2005-2006. These include outbreaks linked to swimming pools, spas, lakes, rivers, and ocean water. Almost half (60 outbreaks or 45 percent) were caused by Cryptosporidium, an extremely chlorine tolerant parasite. The increase during the two-year span is largely due to increases in outbreaks associated with Cryptosporidium. Reversing this trend will require improvements in swimming pool disinfection and operation, pool regulations and enforcement, and swimmer hygiene.

These healthy swimming steps can help stop the spread of germs:

  • Don't swim when you have diarrhea. You can spread germs in the water and make other people sick.
  • Don't swallow the pool water. Avoid getting water in your mouth.
  • Practice good hygiene. Shower with soap before swimming and wash your hands after using the toilet or changing diapers. Germs on your body end up in the water.

In addition, during 2007-2008, more than 4,000 cases of illnesses and injuries were caused by pool chemicals annually. These illnesses and injuries were linked to both private and public pools and often can be prevented by good chemical handling practices.

Eight fatal cases of primary amebic meningoencephalitis, a very rare and deadly brain infection caused by the freshwater ameba Naegleria fowleri occurred during 2007-2008. These cases were all linked to exposure to untreated fresh water, such as lakes and ponds. The only certain way to prevent these infections is to refrain from water-related activities in or with warm freshwater. However, you might reduce your risk when swimming in warm, shallow freshwater by avoiding warm freshwater during periods when the temperature is high and water levels are low, holding your nose or using nose clips, and avoiding digging in or stirring up the sediment.

Outbreaks associated with drinking water:

From January 2007-December 2008, 23 states and Puerto Rico reported 36 outbreaks associated with drinking water. These outbreaks led to 4,128 cases of illness and three deaths. More than half of the drinking water–associated outbreaks reported during the 2007-2008 surveillance period were associated with untreated or inadequately treated ground water, indicating that contamination of ground water remains an important public health problem.

Outbreaks caused by bacteria, viruses, parasites, and chemicals were reported. Legionella alone accounted for one-third of the outbreaks associated with drinking water. Legionella can cause severe respiratory illness and leads to 8,000 to 18,000 hospitalizations per year.

To read both reports, go to

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