Almost 1800 sickened: It’s summer (up north), but beware the water

Outbreaks of illness associated with recreational water use result from exposure to chemicals or infectious pathogens in recreational water venues that are treated (e.g., pools and hot tubs or spas) or untreated (e.g., lakes and oceans).

caddyshackFor 2011–2012, the most recent years for which finalized data were available, public health officials from 32 states and Puerto Rico reported 90 recreational water–associated outbreaks to CDC’s Waterborne Disease and Outbreak Surveillance System (WBDOSS) via the National Outbreak Reporting System (NORS).

The 90 outbreaks resulted in at least 1,788 cases, 95 hospitalizations, and one death. Among 69 (77%) outbreaks associated with treated recreational water, 36 (52%) were caused by Cryptosporidium. Among 21 (23%) outbreaks associated with untreated recreational water, seven (33%) were caused by Escherichia coli (E. coli O157:H7 or E. coli O111). Guidance, such as the Model Aquatic Health Code (MAHC), for preventing and controlling recreational water–associated outbreaks can be optimized when informed by national outbreak and laboratory (e.g., molecular typing of Cryptosporidium) data.

A recreational water–associated outbreak is the occurrence of similar illnesses in two or more persons, epidemiologically linked by location and time of exposure to recreational water or recreational water–associated chemicals volatilized into the air surrounding the water. Public health officials in the 50 states, the District of Columbia, U.S. territories, and Freely Associated States* voluntarily report outbreaks of recreational water–associated illness to CDC. In 2010, waterborne outbreaks became nationally notifiable. This report summarizes data on recreational water–associated outbreaks electronically reported by October 30, 2014 to CDC’s WBDOSS ( for 2011 and 2012 via NORS.† Data requested for each outbreak include the number of cases,§ hospitalizations, and deaths; etiology; setting (e.g., hotel) and venue (e.g., hot tub or spa) where the exposure occurred; earliest illness onset date; and illness type. All outbreaks are classified according to the strength of data implicating recreational water as the outbreak vehicle (1). ¶Outbreak reports classified as Class I have the strongest supporting epidemiologic, clinical laboratory and environmental health data, and those classified as Class IV, the weakest. Classification does not assess adequacy or completeness of investigations.** Negative binomial regression (PROC GENMOD in SAS 9.3 [Cary, NC]) was used to assess trends in the number of outbreaks over time.

For the years 2011 and 2012, public health officials from 32 states and Puerto Rico reported 90 recreational water–associated outbreaks ( (Figure 1), which resulted in at least 1,788 cases, 95 (5%) hospitalizations, and one death. Etiology was confirmed for 73 (81%) outbreaks: 69 (77%) outbreaks were caused by infectious pathogens, including two outbreaks with multiple etiologies, and four (4%) by chemicals (Table). Among the outbreaks caused by infectious pathogens, 37 (54%) were caused by Cryptosporidium. On the basis of data reported to CDC, 37 (41%) of the 90 outbreak reports were categorized as class IV.

Outbreaks associated with treated recreational water accounted for 69 (77%) of the 90 outbreaks reported for 2011–2012, and resulted in at least 1,309 cases, 73 hospitalizations, and one reported death. The median number of cases reported for these outbreaks was seven (range: 2–144 cases). Hotels (e.g., hotel, motel, lodge, or inn) were the setting of 13 (19%) of the treated recreational water–associated outbreaks. Twelve (92%) of these 13 outbreaks started outside of June–August; ten (77%) were at least in part associated with a spa. Among the 69 outbreaks, 36 (52%) were caused by Cryptosporidium. The 69 outbreaks had a seasonal distribution, with 42 (61%) starting in June–August (Figure 1). Acute gastrointestinal illness was the disease manifestation in 34 (81%) of these summer outbreaks, with Cryptosporidium causing 32 (94%) of them. Since 1988, the year that the first U.S. treated recreational water–associated outbreak of cryptosporidiosis was detected (2,3) (Figure 2), the number of these outbreaks reported annually (range: 0–40 outbreaks) has significantly increased (negative binomial regression; p<0.001). Incidence of these cryptosporidiosis outbreaks has also, at least in part, driven the significant increase (negative binomial regression; p<0.001) in the overall number of recreational water–associated outbreaks reported annually (range: 6–84).

caddyshack.pool.poop-1For 2011–2012, 21 (23%) outbreaks were associated with untreated recreational water. These outbreaks resulted in at least 479 cases and 22 hospitalizations. The median number of cases reported for these outbreaks was 16 (range: 2–125). Twenty (95%) of these outbreaks were associated with fresh water; 18 (86%) began in June–August; and seven (33%) were caused by E. coli O157:H7 or O111. One outbreak associated with exposure to cyanobacterial toxins was reported.


Cryptosporidium continues to be the dominant etiology of recreational water–associated outbreaks. Half of all treated recreational water–associated outbreaks reported for 2011–2012 were caused by Cryptosporidium. Among treated recreational water–associated outbreaks of gastrointestinal illness that began in June–August, >90% were caused by Cryptosporidium, an extremely chlorine-tolerant parasite that can survive in water at CDC-recommended chlorine levels (1–3 mg/L) and pH (7.2–7.8) for >10 days (4). In contrast, among 14 untreated recreational water–associated outbreaks of gastrointestinal illness starting in June–August, 7% (one) were caused by Cryptosporidium. The decreased diversity of infectious etiologies causing treated recreational water–associated outbreaks is likely a consequence of the aquatic sector’s reliance on halogen disinfection (e.g., chlorine or bromine) and maintenance of proper pH, which are well documented to inactivate most infectious pathogens within minutes (5). Continued reporting of treated recreational water–associated outbreaks caused by chlorine-intolerant pathogens (e.g., E. coli O157:H7 and norovirus) highlights the need for continued vigilance in maintaining water quality (i.e., disinfectant level and pH), as has been recommended for decades (5).

In the United States, codes regulating public treated recreational water venues are independently written and enforced by individual state or local agencies; the consequent variation in the codes is a potential barrier to preventing and controlling outbreaks associated with these venues. In August 2014, CDC released the first edition of MAHC (, a comprehensive set of science-based and best-practice recommendations to reduce risk for illness and injury at public, treated recreational water venues. MAHC represents the culmination of a 7-year, multi-stakeholder effort and is an evolving resource that addresses emerging public health threats, such as treated recreational water-associated outbreaks of cryptosporidiosis, by incorporating the latest scientifically validated technologies that inactivate or remove infectious pathogens. For example, MAHC recommends additional water treatment (e.g., ultraviolet light or ozone) to inactivate Cryptosporidium oocysts at venues where WBDOSS data indicate there is increased risk for transmission. MAHC recommendations can be voluntarily adopted, in part or as a whole, by state and local jurisdictions.

The number of reported untreated recreational water–associated outbreaks confirmed or suspected to be caused by cyanobacterial toxins has decreased, from 11 (2009–2010) to one (2011–2012) (6). This decrease is likely the result of a decrease in outbreak reporting rather than a true decrease in incidence. CDC is currently developing a mechanism for reporting algal bloom–associated individual cases through NORS to better characterize their epidemiology.

The findings in this report are subject to at least two limitations. First, the outbreak counts presented are likely an underestimate of actual incidence. Many factors can present barriers to the detection, investigation, and reporting of outbreaks: 1) mild illness; 2) small outbreak size; 3) long incubation periods; 4) wide geographic dispersion of ill swimmers; 5) transient nature of contamination; 6) setting or venue of outbreak exposure (e.g., residential backyard pool); and 7) potential lack of communication between those who respond to outbreaks of chemical etiology (e.g., hazardous materials personnel) and those who usually report outbreaks (e.g., infectious disease epidemiologists). Second, because of variation in public health capacity and reporting requirements across jurisdictions, those reporting outbreaks most frequently might not be those in which outbreaks most frequently occur.

Increasingly, molecular typing tools are being employed to understand the epidemiology of waterborne disease and outbreaks. Most species and genotypes of Cryptosporidium are morphologically indistinguishable from one another, and only molecular methods can distinguish species and subtypes and thereby elucidate transmission pathways (7,8). Systematic national genotyping and subtyping of Cryptosporidium in clinical specimens and environmental samples through CryptoNet ( can identify circulating Cryptosporidium species and subtypes and help identify epidemiologic linkages between reported cases. Molecular typing could substantially help elucidate cryptosporidiosis epidemiology in the United States and inform development of future guidance to prevent recreational water–associated and other outbreaks of cryptosporidiosis (9,10).


State, territorial, local, and Freely Associated State waterborne disease coordinators, epidemiologists, and environmental health personnel; Lihua Xiao, Sarah A. Collier, Kathleen E. Fullerton, Division of Foodborne, Waterborne, and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, CDC.

1Division of Foodborne, Waterborne, and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, CDC; 2Environmental Protection Agency; 3Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee.

Corresponding author: Michele C. Hlavsa,, 404-71

Outbreaks of Illness Associated with Recreational Water — United States, 2011–2012

Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report

Michele C. Hlavsa, MPH; Virginia A. Roberts, MSPH; Amy M. Kahler, MS; Elizabeth D. Hilborn, DVM; Taryn R. Mecher, MPH; Michael J. Beach, PhD; Timothy J. Wade, PhD; Jonathan S. Yoder, MPH

Chlorine don’t do much against crypto: Claims Australian water park made kids

Townsville City Council says the Strand water park will reopen for regular operation tomorrow after claims kids were struck down with vomiting and diarrhea after playing at the popular attraction.

Strand water parkThe council said initial results from routine water samples indicated no issue with the water, with further results expected on Friday.

“The park is closed today for regular weekly maintenance and as a precaution additional chlorine will be flushed through the filtration system,” a spokeswoman said.

“Regular chlorine checks are also undertaken at the park four times per day and water testing is conducted on a weekly basis.

“Council has contacted health authorities who have not reported any spike in illness.”

Rosslea mum Jaye Dee Sullivan said she and daughter Lilyan Flaherty, 3, spent last night in the emergency department after both became severely ill with vomiting and diarrhea.

She said the waiting room had been full of other families suffering from the same symptoms.

It turned out all had been to the popular water park on Australia Day.

“Everybody else said ‘yes’ and put their hands up,” she said.

Is doggy doo-doo polluting your water?

The stuff is everywhere.We know we’re supposed to clean up after our best friends—but a lot of us don’t.

banner-petAccording to Take Part, scientists at the U.S. Environmental Protection Agency (EPA) have developed new DNA testing to determine how much doggie doo-doo is in our waterways—and what that means for our health.

Dog waste contains bacteria such as E. coli, Giardia and parasites. When we don’t pick it up, that bacteria can run off into drain systems for lakes, rivers and ocean, triggering waterborne disease such as stomach virus or diarrhea.

But how responsible are irresponsible dog owners for our oft-polluted waters?

“The extent of water fecal matter attributable to dogs is poorly understood, in part due to the lack of reliable technologies able to discriminate between dog and other sources of fecal pollution,” Cathy Milbourn, an EPA spokesperson, wrote in an email.

The study, she said, was done in the hopes of creating tools that could give scientists and watershed managers a way to identify dog fecal matter when present in bodies of water.

To test their methods, the scientists tested storm water samples from an urban rainwater garden often visited by domestic dogs.

The test identifies 12 genetic markers commonly found in most dog fecal bacteria samples—but not those found in human waste.

“Findings suggested that these new assays (tests) may be helpful for the identification and quantification of aquatic fecal contaminants originating from canines,” Milbourn wrote.

The results were published last month in the journal Environmental Science and Technology and is available for anyone—such as health departments, government officials or watershed managers.

But before we can point the finger at canines, Milbourn said there are a few caveats with the testing. Right now, the tests aren’t able to measure how much of the disease-causing agents could be affecting local waterways.

“It is important to note that the development and publication of these methods is just the first step in a series of research needed to characterize the extent of canine fecal pollution in waterways,” Milbourn wrote.

Traces of Norovirus found in Finish patients’ tests

The first laboratory tests of fecal samples from individuals who went swimming around Tampere have yielded signs that the virus remains present in local waterways.  

norovirus-2Patient specimens were obtained from a total of 18 people, 15 of whose tests showed positive for the virus.

Tampere city’s Environmental Health Director Merja Bojang says that this indicates that the norovirus has spread though bathers from one beach to another.

Tampere City authorities want to identify the causes and consequences of the epidemic, which causes an upset stomach. The city website now hosts an online form inviting feedback from visitors to Tampere beaches between July 21 and August 6 – both those who remained healthy and those who fell ill.

They also hope to hear back from respondents who have earlier used the form or the telephone service to log details of their illness. It’s hoped that each individual would fill out their own form.

The electronic questionnaire can be answered until Friday, August 22.

53 sickened; contaminated water led to norovirus outbreak in NZ last year

An acute norovirus outbreak in the Cardrona township of New Zealand during last year’s ski season was caused by sewage contamination of drinking water and the wider environment, a peer-reviewed investigation says.

The month-long outbreak of norovirus that caused at least 53 cases of diarrhoea, vomiting norovirus-2and nausea was only the third documented waterborne transmission in New Zealand.

Crucially, the report also says a strategy is “urgently required” to decrease environmental contamination of drinking water supplies, improve sewage disposal and manage drinking water.

The report, in the New Zealand Medical Association journal by Dr Derek Bell, Susan Jack and Joanne Hewitt, discusses the investigation of the waterborne gastroenteritis outbreak that infected at least 53 people in and around Cardrona in mid-August and early September last year.

The Southern District Health Board yesterday confirmed the article, which mentions a hotel and resort in “southern New Zealand”, referenced the Cardrona township, the hotel and accommodation providers in the village.

Cardrona Hotel, under new management earlier this year, has a supply from a bore and the hotel water system supplies water to neighbouring properties via 11 water access points. Another township accommodation provider, Benbrae, has an independent water supply and sewage system.

Public Health South investigated, interviewing 66 people, collecting samples, visiting the site, inspecting premises and water supplies.

The illness lasted, on average, for 36 hours and the cases included 12 Cardrona residents.

Hotel drinking water samples and the hotel bore were positive for norovirus, a drinking tap from the neighbouring accommodation was positive, and river samples and water downstream of the wastewater disposal field were positive.

A supply runs from a 14-metre deep bore, the water is chlorinated and pumped to holding tanks, then gravity-fed to the hotel and other access points. There was inadequate chlorination, an ineffective chlorine pump and there was surface flooding contamination, the article says.

Crypto control: NYC opens world’s largest UV drinking water treatment facility

The world’s largest ultraviolet drinking water treatment facility, the $1.5 billion Catskill/Delaware UV Facility, provides treatment specifically for Cryptosporidium and Giardia microorganisms in the drinking water consumed by more than 9 million residents of the city and parts of Westchester County.

The 270,000-square-foot facility is designed to treat more than 2 billion gallons of water each day, more than three times the capacity of the next-Catskill:Delaware UV Facilitylargest municipal UV treatment facility in the United States, which is under construction in Los Angeles, according to DEP.

A 1993 Cryptosporidium outbreak in Milwaukee caused new federal regulations for treating drinking water to be created, because Cryptosporidium is resistant to disinfection with chlorine. Researchers then discovered that exposing water to low levels of UV light makes Cryptosporidium and Giardia harmless to human beings.

The Catskill/Delaware UV Facility 2006 began treating water in late 2012 as its construction continued; the construction is now substantially complete. The facility has 56 UV units and 11,760 UV bulbs overall.

Toilet-to-tap: don’t drink poop, unless it’s treated really, really well

Don’t eat poop, and if you do, cook it.

Australians may be trying out don’t drink poop, unless it’s safely treated.

The Sydney Morning Herald reports that Australians will be encouraged to embrace treated sewage for drinking in the largest-ever bid to overcome the”yuck factor” and push the contentious option onto the national agenda.

A $10 million drive, partly funded by the federal government, aims to convince the public that introducing recycled water to drinking supplies is a palatable, cost-effective alternative to measures such as desalination.

The ”engagement strategy” will target households, students, politicians and the water industry.

Public scepticism and fears over health risks have traditionally kept the toilet-to-tap concept off the political agenda.

The chair of the project’s research advisory committee, Ian Law, said recycled water for drinking should be examined before crisis loomed ”when dams are full … so we have the ducks in a row when the next drought comes”.

The project, led by the University of NSW, will develop a national engagement program to show that recycled water is safe and reliable. It will include devising education programs, a social media campaign and MutantFishdemonstration projects where the public could see wastewater being treated. Similar schemes overseas allow visitors to sample the water.

The Brisbane-based Australian Water Recycling Centre of Excellence is co-ordinating the project, which will also examine recycled stormwater.

In a terrible example of risk communication, Mr Law said, ”There is nothing more powerful than an informed public,” he said, adding those who drank recycled water wouldn’t ‘”grow five heads.”

The target audience will remember the five-heads bit.