Skip directly to search Skip directly to A to Z list Skip directly to site content
CDC Home

Appendix B

Descriptions of Select Waterborne Disease Outbreaks Associated with Recreational Water Use

Month

Year

State

Etiology

No. of cases

Outbreak description

Bacteria

February

2008

Wisconsin

Pseudomonas aeruginosa

18

After spending time in a hotel/motel pool and spa, 17 persons reported having a rash and one person reported an ear infection. A swab of one person's skin lesion yielded P. aeruginosa. A case-control study found a statistically significant association between using the spa on a given Saturday and the development of symptoms. An environmental health investigation noted that no water quality readings were recorded on the Saturday that case-patients used the spa.

March

2008

Florida

Legionella

5

The results of a matched case-control study epidemiologically linked five travel-associated cases of legionellosis to spa exposure at a hotel/motel. The spa had two cartridge filters and an automatic chlorine feeder. The environmental health investigation noted that the pool and spa had free chlorine levels of <0.5 mg/L (or parts per million [ppm]) and the cartridge filters were insufficient for the size of the spa. The maintenance logs for the spa were not available. Environmental water samples from the spa, hotel boilers, and a room air conditioner all tested negative for Legionella.

Viruses

May

2007

Idaho

Norovirus genogroup II

50

After exposure to a community pool and wading pool, six persons submitted stool specimens that tested positive for norovirus genogroup II. The pools had a combined filtration system. An investigation identified multiple contributing factors, including high bather load, inaccessible bathroom facilities, and lack of oversight by management to handle fecal incidents.

July

2008

Connecticut

Norovirus genogroup I

16

After exposure to a lake that was used by diaper-aged children, six persons submitted stool specimens that tested positive for norovirus genogroup I. A fecal incident and stagnant water were suspected as contributing factors in the outbreak. A case-control study found that the odds of developing gastrointestinal symptoms were significantly higher for persons who swam in the lake on a particular day, swam in the water for more than an hour, or swallowed lake water compared with persons who did not report these exposures. Swimming >12 feet from shore also was associated with an increased odds of illness (p=0.0004).

Parasites

June

2007

New Mexico

Schistosomes

12

A medical provider's office reported multiple individuals seen for rashes diagnosed as cercarial dermatitis ("swimmer's itch") after spending time at a freshwater lake. The outbreak investigation included: case interviews, environmental assessment, and testing. Cases occurred among individuals who entered the water from the shoreline and did not occur in individuals who entered the water directly from a boat. Cercariae were isolated from snails collected along the shoreline. Low water levels 2 years earlier supported increased vegetation and large snail populations along the shoreline. Warning signs posted at the lake in English and Spanish listed allergic reaction symptoms and prevention measures.

July

2007

Oklahoma

Oklahoma

C. hominis C. parvum

93

17

Molecular subtyping of Cryptosporidium isolates led public health officials to determine that two distinct outbreaks of cryptosporidiosis had occured in neighboring counties during the same month. Persons affected by the first outbreak reported swimming in a pool that was the only publicly accessible swimming pool in the community, and none of the persons with laboratory-confirmed cases reported swimming in another pool. Cryptosporidium oocysts isolated from stool specimens of 11 patients and four liters of pool filter backwash were subtyped as C. hominis. Persons affected by the second outbreak stayed in state park cabins during a week-long period in mid-July. A retrospective cohort study implicated the park's pool. Molecular typing of stool specimens and pool backwash identified C. parvum and provided strong supporting evidence that the cases were not part of the first outbreak.

Month

Year

State

Etiology

No. of cases

Outbreak description

August

2007

Iowa

Cryptosporidium

34

County public health staff responded quickly to prevent a focal cryptosporidiosis outbreak from becoming communitywide following notification of two laboratory-confirmed cases in children with recent swimming pool exposures. Public health staff immediately initiated case investigations and active cryptosporidiosis surveillance. Local health-care providers were sent a health alert containing information about how to diagnose and report cryptosporidiosis cases. Child care providers were sent guidance about disease prevention and control measures. The environmental health staff worked closely with local pools, starting on the day that the first two cases were reported. Multiple pools were hyperchlorinated immediately. A fact sheet also was shared with several neighboring counties for distribution to pool operators.

July

2008

New Mexico

C. hominis

89

Confirmed cases of cryptosporidiosis were identified among competitive swimmers who swam at a community aquatic facility. At least one patient swam while symptomatic and participated in competitions with hundreds of swimmers. Working closely with state and local partners, the New Mexico Department of Health coordinated the health communications, epidemiologic investigation, and environmental health response to the outbreak. This included hyperchlorination of all pools in the aquatic facility as well as any other pools that infectious swimmers had used. A total of 34% of ill persons (including competitive swimmers, lifeguards, or swim team coaches) reported recreational water activity while symptomatic or in the 2 weeks following symptom resolution. Stool specimens from multiple persons and recreational water tested positive for C. hominis. Clinical isolates were of the same subtype.

July

2008

Arizona

C. hominis

9

Four laboratory-confirmed cases of C. hominis infection were linked to the same interactive fountain. The interactive fountain was not found to have any violations upon initial inspection. Staff complied with health department recommendations. Water from the interactive fountain tested positive for Cryptosporidium both before and after disinfection guidelines were applied; follow-up testing is not recommended by CDC because nonviable oocysts present in the treated water might lead to a positive test result via molecular testing. Molecular subtyping determined that this outbreak was unique from two concurrent recreational water--associated outbreaks in Arizona. An ultraviolet disinfection system was added to supplement the bromine disinfection system.

Chemicals/Toxins

January

2008

Illinois

Chlorine

20

At least 20 persons were hospitalized and an unknown number of people were injured after exposure to chlorine at an indoor waterpark. Case counts and symptom data were based on fire department records. The automatic controller that managed pool disinfectant and pH levels failed. Pool staff did not recognize the problem during routine testing. The free chlorine and pH levels of the wading pool measured 18 mg/L and 8.3, respectively, on the day that the event occurred.


Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services.

References to non-CDC sites on the Internet are provided as a service to MMWR readers and do not constitute or imply endorsement of these organizations or their programs by CDC or the U.S. Department of Health and Human Services. CDC is not responsible for the content of pages found at these sites. URL addresses listed in MMWR were current as of the date of publication.

All MMWR HTML versions of articles are electronic conversions from typeset documents. This conversion might result in character translation or format errors in the HTML version. Users are referred to the electronic PDF version (http://www.cdc.gov/mmwr) and/or the original MMWR paper copy for printable versions of official text, figures, and tables. An original paper copy of this issue can be obtained from the Superintendent of Documents, U.S. Government Printing Office (GPO), Washington, DC 20402-9371; telephone: (202) 512-1800. Contact GPO for current prices.

**Questions or messages regarding errors in formatting should be addressed to mmwrq@cdc.gov.

 
USA.gov: The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Rd. Atlanta, GA 30333, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC–INFO
A-Z Index
  1. A
  2. B
  3. C
  4. D
  5. E
  6. F
  7. G
  8. H
  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z
  27. #