CDC Urges Action to Prevent Cryptosporidiosis Outbreaks

ATLANTA, July 30 -- A spike in outbreaks of cryptosporidiosis in 2006 has spurred the CDC to launch an initiative this summer to improve the safety of swimming pools and other recreational water facilities.

The CDC identified 18 cryptosporidiosis outbreaks in 2006, according to a report in the July 27 issue of Morbidity and Mortality Weekly Report. That compares with five outbreaks in 2003 and seven in 2004, the last two years for which there is complete data.

Contaminated water in recreational facilities is suspected in most, if not all, of the outbreaks. Although limited testing of implicated water sources failed to confirm the presence of Cryptosporidium, CDC investigators concluded that the epidemiologic findings "implicated contaminated recreational water as the source of the outbreaks."

Concerned lest the 2006 spike become a trend, the CDC has joined with public health officials and representatives of aquatic interests to launch the Healthy Swimming initiative to improve recreational water safety. Information on the initiative is available at http://www.cdc.gov/healthyswimming.

To reduce the risk of cryptosporidiosis associated with recreational water venues, the CDC recommends the following:

The general public:

• Don't swim during episodes of diarrhea or for two weeks afterward
• Avoid swallowing pool water
• Practice proper hygiene, particularly with respect to hand washing

Health care providers:

• Report cryptosporidiosis cases to local health departments
• Collect stool samples and request Cryptosporidium testing, as indicated
• Advise patients to refrain from swimming during episodes of diarrhea and for two weeks afterward
• Remind parents that children with diarrheal disease should not enter the water at recreational facilities

"A multifaceted approach for prevention of cryptosporidiosis in treated water venues must address operational, technological, and behavioral factors related to recreational water use," CDC investigators stated.

The MMWR report described five laboratory-confirmed cryptosporidiosis outbreaks involving recreational water exposure in 2006:

• In Douglas County, Colo., 12 of 21 people attending a party at a community water park developed diarrhea, vomiting, or abdominal cramps. Twelve of 17 people exposed to the water reported illness, compared with none of the people who were not exposed to the water. All seven stool samples collected for examination tested positive for Cryptosporidium, and further testing on four samples revealed the same genotype of Cryptosporidium hominis.
• In Tazewell County, Ill., two brothers developed cryptosporidiosis after attending a private day camp with a swimming pool. CDC interviews with 105 camp attendees, staff, and volunteers showed that 56 reported diarrhea or vomiting, including 56 of 63 people who entered the pool versus none who did not enter the pool. Of eight stool samples collected, seven contained Cryptosporidium, including four with the same C. hominis genotype.
• In two Louisiana parishes, 35 cases of cryptosporidiosis were reported to public health officials. Interviews with 29 patients and 29 matched controls showed that exposure to water at one recreational park was the only exposure significantly associated with cryptosporidiosis.
• A total of 123 cases of laboratory-confirmed cryptosporidiosis were reported in 2006 to the South Carolina public health authorities, including 88 in the Charleston area. Interviews with 85 of the affected individuals showed that 81 reported water exposures at parks, swimming pools, and day care centers.
• Wyoming health authorities received information on 34 cases of laboratory-confirmed cryptosporidiosis from Campbell and Crook counties. Interviews with 26 patients and 41 matched controls revealed that cryptosporidiosis was significantly associated with water exposure at public swimming pools and at a local reservoir.

Unlike bacteria, Cryptosporidium oocysts are resistant to chlorine disinfection and can survive for days in treated recreational water facilities, the CDC authors noted.

The parasite, which has an incubation period of up to 12 days, is the leading cause of gastroenteritis outbreaks associated with treated recreational water venues, accounting for about 60% of outbreaks reported to the CDC during 1995-2004.

In four of the five cases described in the CDC report, available records reflected adherence to recommendations for disinfection and chlorination. The observation emphasized that "conventional chlorination and filtration of swimming pools and water parks are inadequate to control cryptosporidiosis and transmission of recreational water illness."

Improved disinfection technology that inactivates Cryptosporidium and greater public awareness of healthy swimming practices are two public health interventions that might reduce transmission of the parasite, the CDC investigators concluded.