High serological response to Cryptosporidium-specific antigens in the Czech Republic and its association with water supply.

A survey was conducted in the Czech Republic to determine whether serological responses to the 15/17-kDa and 27-kDa Cryptosporidium antigens had changed since the end of the communist era and if these responses were associated with drinking water sources. Sera from 301 blood donors residing in six areas served by various sources of drinking water were analysed by Western Blot (mini-immunoblots) to measure the IgG response. The intensity of response and percentage of persons with a strong response to the 27-kDa, but not the 15/17-kDa, antigen were higher than found 20 years earlier. A strong response to both the 15/17- and 27-kDa-antigens was higher than reported in other countries, and the probability of persons having a strong response was greater in areas with surface water sources than river-bank infiltration. Few cases of cryptosporidiosis were reported in spite of these high responses to Cryptosporidium antigens. These responses suggest a chronic low-level exposure from several sources that may be affording protection against symptoms and illness. Although strong serological responses were associated with surface water sources, drinking water is not likely to be the most important exposure for Cryptosporidium in the Czech Republic.

Causes of outbreaks associated with drinking water in the United States from 1971 to 2006.

Since 1971, the CDC, EPA, and Council of State and Territorial Epidemiologists (CSTE) have maintained the collaborative national Waterborne Disease and Outbreak Surveillance System (WBDOSS) to document waterborne disease outbreaks (WBDOs) reported by local, state, and territorial health departments. WBDOs were recently reclassified to better characterize water system deficiencies and risk factors; data were analyzed for trends in outbreak occurrence, etiologies, and deficiencies during 1971 to 2006. A total of 833 WBDOs, 577,991 cases of illness, and 106 deaths were reported during 1971 to 2006. Trends of public health significance include (i) a decrease in the number of reported outbreaks over time and in the annual proportion of outbreaks reported in public water systems, (ii) an increase in the annual proportion of outbreaks reported in individual water systems and in the proportion of outbreaks associated with premise plumbing deficiencies in public water systems, (iii) no change in the annual proportion of outbreaks associated with distribution system deficiencies or the use of untreated and improperly treated groundwater in public water systems, and (iv) the increasing importance of Legionella since its inclusion in WBDOSS in 2001. Data from WBDOSS have helped inform public health and regulatory responses. Additional resources for waterborne disease surveillance and outbreak detection are essential to improve our ability to monitor, detect, and prevent waterborne disease in the United States.

Enteric illness risks before and after water treatment improvements.

This study evaluated whether occurrence of acute gastrointestinal illnesses declined after filtration and ozonation were added to a previously unfiltered, chlorinated high-quality surface water source in a northwest United States city. Enteric and other illnesses were recorded for two 6-month periods for control and intervention sites in the same city. During phase 1, chlorinated, unfiltered drinking water for both sites was obtained from protected watersheds. During phase 2, the intervention site received chlorinated, filtered and ozonated drinking water. The water was not altered in the control site. No overall differences were found in the risk of any of the illnesses after the new water treatment plant was completed. There was a significantly increased risk of diarrhoea and highly credible gastrointestinal illness in participants with three or more episodes of the same type of illness during phase 1.

Estimates of endemic waterborne risks from community-intervention studies.

The nature and magnitude of endemic waterborne disease are not well characterized in the United States. Epidemiologic studies of various designs can provide an estimate of the waterborne attributable risk along with other types of information. Community drinking water systems frequently improve their operations and may change drinking water treatment and their major source of water. In the United States, many of these treatment changes are the result of regulations promulgated under the Safe Drinking Water Act. A community-intervention study design takes advantage of these "natural" experiments to assess changes in health risks. In this paper, we review the community-intervention studies that have assessed changes in waterborne gastroenteritis risks among immunocompetent populations in industrialized countries. Published results are available from two studies in Australia, one study in the United Kingdom, and one study in the United States. Preliminary results from two other US studies are also available. Although the current information is limited, the risks reported in these community-intervention studies can help inform the national estimate of endemic waterborne gastroenteritis. Information is provided about endemic waterborne risks for unfiltered surface water sources and a groundwater under the influence of surface water. Community-intervention studies with recommended study modifications should be conducted to better estimate the benefits associated with improved drinking water treatment.

Observational epidemiologic studies of endemic waterborne risks: cohort, case-control, time-series, and ecologic studies.

Observational studies have assessed endemic waterborne risks in a number of countries. Time-series analyses associated increased water turbidity with increased gastroenteritis risks in several public water systems. Several cohort studies reported an increased risk of gastroenteritis in populations using certain public or individual water systems. Although several case-control studies found increased waterborne risks, they also found increased risks associated with other exposures. An increased risk of campylobacteriosis was associated with drinking untreated water from non-urban areas and some tap waters; other significant risks included contaminated poultry and foreign travel. Increased risks of cryptosporidiosis and giardiasis were associated with drinking water in some populations; other risk factors included foreign travel, day care exposures, and swimming. These observational studies provide evidence that some populations may be at an increased risk of endemic or sporadic illness from waterborne exposures, but not all studies found an increased risk. Differences in waterborne risks may be due to differences in water quality. System vulnerabilities and contamination likely differed in the areas that were studied. The information from these studies may help inform estimates of waterborne illness for the US population but is inadequate to estimate a population attributable risk.

Workshop summary: estimating waterborne disease risks in the United States.

A workshop was held in Atlanta on July 7-8, 2005, to evaluate the epidemiologic and other information available for estimating endemic waterborne illness risks in the United States. Each paper written for this special issue was discussed and fourteen recommendations were made based on the discussion. In addition, seven major data gaps were identified as being key to reducing the uncertainty associated with a calculation of a national estimate. This summary is provided to help regulatory officials, public health professionals, and others better understand the health measures being estimated and adequacy of the current risk information. The summary also provides a blueprint for researchers interested in studying the endemic and epidemic risks of microbes in drinking water.

Assessing waterborne risks: an introduction.

Information in this paper can help readers evaluate the results of epidemiologic studies of waterborne disease risks. It is important that readers understand the various epidemiologic study designs, their strengths and limitations, and potential biases. Terminology used by epidemiologists to describe disease risks can be confusing. Thus, readers should not only evaluate the adequacy of the information to estimate waterborne risks but should also understand how the risk was estimated. For example, one author's definition of attributable risk may be quite different from another author's in terms of the population to which the risk may apply and how it should be interpreted.

Waterborne outbreaks reported in the United States.

Epidemic waterborne risks are discussed in this paper. Although the true incidence of waterborne illness is not reflected in the currently reported outbreak statistics, outbreak surveillance has provided information about the important waterborne pathogens, relative degrees of risk associated with water sources and treatment processes, and adequacy of regulations. Pathogens and water system deficiencies that are identified in outbreaks may also be important causes of endemic waterborne illness. In recent years, investigators have identified a large number of pathogens responsible for outbreaks, and research has focused on their sources, resistance to water disinfection, and removal from drinking water. Outbreaks in surface water systems have decreased in the recent decade, most likely due to recent regulations and improved treatment efficacy. Of increased importance, however, are outbreaks caused by the microbial contamination of water distribution systems. In order to better estimate waterborne risks in the United States, additional information is needed about the contribution of distribution system contaminants to endemic waterborne risks and undetected waterborne outbreaks, especially those associated with distribution system contaminants.

The role of disease burden measures in future estimates of endemic waterborne disease.

The 1996 Safe Drinking Water Act amendments require the US Environmental Protection Agency and the Centers for Disease Control and Prevention to develop a national estimate of the occurrence of waterborne infectious disease that is attributable to public drinking water systems in the United States. Much of the information for developing the national estimate will be derived from epidemiologic data, and the primary outcome of this effort will be an estimate of the number of cases of gastrointestinal illness. While quantifying the number of these cases provides some measure of waterborne disease impact, the usefulness of this measure may be limited because the full spectrum of societal impact also involves consideration of the additional effects of these diseases such as hospitalization costs and lost productivity. If decision-makers wish to compare the impact of waterborne infectious diseases to the impact of some other public health concern (e.g. to aid in resource allocation decisions), then a comparison of case numbers may prove inadequate. Case numbers alone do not provide sufficient information about the severity of different illnesses. Society may value the avoidance of a few cases of severely debilitating illness more than it values the avoidance of many cases of mild illness. In order to compare disparate public health concerns, "burden of disease" measures that incorporate indicators of disease severity, costs, or societal values may prove essential for some types of decisions. We describe epidemiologic measures of severity, quality adjusted life years (QALYs), disability adjusted life years (DALYs), willingness-to-pay, and cost-of-illness methods commonly used for burden of disease estimates, and discuss how some of these summary measures of burden might be used for waterborne disease estimates.

Surveillance for waterborne-disease outbreaks--United States, 1999-2000.

PROBLEM/CONDITION: Since 1971, CDC, the U.S. Environmental Protection Agency (EPA), and the Council of State and Territorial Epidemiologists (CSTE) have maintained a collaborative surveillance system for the occurrences and causes of waterborne-disease outbreaks (WBDOs).This surveillance system is the primary source of data concerning the scope and effects of waterborne diseases on persons in the United States. REPORTING PERIOD COVERED: This summary includes data regarding outbreaks occurring during January 1999-December 2000 and previously unreported outbreaks occurring in 1995 and 1997. DESCRIPTION OF THE SYSTEM: The surveillance system includes data for outbreaks associated with drinking water and recreational water. State, territorial, and local public health departments are primarily responsible for detecting and investigating WBDOs and voluntarily reporting them to CDC on a standard form. The unit of analysis for the WBDO surveillance system is an outbreak, not an individual case of a waterborne disease. Two criteria must be met for an event to be defined as a WBDO. First, > or = 2 persons must have experienced a similar illness after either ingestion of drinking water or exposure to water encountered in recreational or occupational settings. This criterion is waived for single cases of laboratory-confirmed primary amebic meningoencephalitis and for single cases of chemical poisoning if water-quality data indicate contamination by the chemical. Second, epidemiologic evidence must implicate water as the probable source of the illness. RESULTS: During 1999-2000, a total of 39 outbreaks associated with drinking water was reported by 25 states. Included among these 39 outbreaks was one outbreak that spanned 10 states. These 39 outbreaks caused illness among an estimated 2,068 persons and were linked to two deaths. The microbe or chemical that caused the outbreak was identified for 22 (56.4%) of the 39 outbreaks; 20 of the 22 identified outbreaks were associated with pathogens, and two were associated with chemical poisoning. Of the 17 outbreaks involving acute gastroenteritis of unknown etiology, one was a suspected chemical poisoning, and the remaining 16 were suspected as having an infectious cause. Twenty-eight (71.8%) of 39 outbreaks were linked to groundwater sources; 18 (64.3%) of these 28 groundwater outbreaks were associated with private or noncommunity wells that were not regulated by EPA. Fifty-nine outbreaks from 23 states were attributed to recreational water exposure and affected an estimated 2,093 persons. Thirty-six (61.0%) of the 59 were outbreaks involving gastroenteritis. The etiologic agent was identified in 30 (83.3%) of 36 outbreaks involving gastroenteritis. Twenty-two (61.1%) of 36 gastroenteritis-related outbreaks were associated with pools or interactive fountains. Four (6.8%) of the 59 recreational water outbreaks were attributed to single cases of primary amebic meningoencephalitis (PAM) caused by Naegleria fowleri. All four cases were fatal. Fifteen (25.4%) of the 59 outbreaks were associated with dermatitis; 12 (80.0%) of 15 were associated with hot tubs or pools. In addition, recreational water outbreaks of leptospirosis, Pontiac fever, and chemical keratitis, as well as two outbreaks of leptospirosis and Pontiac fever associated with occupational exposure were also reported to CDC. INTERPRETATION: The proportion of drinking water outbreaks associated with surface water increased from 11.8% during 1997-1998 to 17.9% in 1999-2000. The proportion of outbreaks (28) associated with groundwater sources increased 87% from the previous reporting period (15 outbreaks), and these outbreaks were primarily associated (60.7%) with consumption of untreated groundwater. Recreational water outbreaks involving gastroenteritis doubled (36 outbreaks) from the number of outbreaks reported in the previous reporting period (18 outbreaks). These outbreaks were most frequently associated with Cryptosporidium parvum (68.2%) in treated water venues (e.g., swimming pools or interactive fountains) and by Escherichia coli O157:H7 (21.4%) in freshwater venues. The increase in the number of outbreaks probably reflects improved surveillance and reporting at the local and state level as well as a true increase in the number of WBDOs. PUBLIC HEALTH ACTION: CDC and others have used surveillance data to identify the types of water systems, their deficiencies, and the etiologic agents associated with outbreaks and evaluated current technologies for providing safe drinking water and safe recreational water. Surveillance data are used also to establish research priorities, which can lead to improved water-quality regulations. Only the groundwater systems under the influence of surface water are required to disinfect their water supplies, but EPA is developing a groundwater rule that specifies when corrective action (including disinfection) is required. CDC and EPA are conducting epidemiologic studies to assess the level of waterborne illness attributable to municipal drinking water in nonoutbreak conditions. Rules under development by EPA--the Ground Water Rule (GWR), the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR), and Stage 2 Disinfection Byproduct Rules (DBPR)--are expected to further protect the public from contaminants and disinfection byproducts in drinking water. Efforts by EPA under the Beaches Environmental Assessment, Closure, and Health (BEACH) program are aimed at reducing the risks for infection attributed to ambient recreational water by strengthening beach standards and testing; providing faster laboratory test methods; predicting pollution; investing in health and methods research; and improving public access to information regarding both the quality of the water at beaches and information concerning health risks associated with swimming in polluted water. EPA's Beach Watch (available at http://www.epa.gov/waterscience/beaches) provides online information regarding water quality at U.S. beaches, local protection programs, and other beach-related programs. CDC partnered with a consortium of local and national pool associations to develop a series of health communication materials for the general public who attend treated recreational water venues and to staff who work at those venues. CDC has also developed a recreational water outbreak investigation toolkit that can be used by public health professionals. All of the CDC materials are accessible at the CDC Healthy Swimming website (http://www.cdc.gov/healthyswimming).

Serological evidence of endemic waterborne cryptosporidium infections.

PURPOSE: Cryptosporidium oocysts are commonly detected in surface-derived drinking water, however, the public health significance of these findings is unclear. This study compared the evidence of prior Cryptosporidium infection for people drinking water derived from surface versus ground water sources. METHODS: This study measured serological responses to two Cryptosporidium antigen groups for blood donors from two midwestern United States cities with different drinking water sources: filtered and chlorinated river water receiving agricultural and domestic sewage upstream versus chlorinated water from an underground aquifer. Initial and nine-month paired serological responses to two Cryptosporidium antigen groups were compared. RESULTS: Initially, donors from the surface water city had a higher relative prevalence (RP) of a serological response (54% vs. 38%, RP = 1.39 (1.21,1.60)). Donors with a detectable baseline response who resided in the surface water city had a higher relative risk (RR) of an increased intensity of response on the follow-up blood draw (15/17-kDa, 40/100 vs. 11/100, RR = 3.78 (1.89,7.58)), (27-kDa 38/100 vs. 18/100, RR = 2.07 (1.31,3.25)). Donors with no baseline response to the 15/17-kDa marker who resided in the surface water city also had a higher risk of serconversion (38/100 vs. 14/100, RR = 2.63 (1.78,3.91)). CONCLUSIONS: These rates of both background and drinking water related Cryptosporidium infections are substantially higher than previously estimated, however, the risk of illness from infection may be lower.

Analysis of serological responses to Cryptosporidium antigen among NHANES III participants.

PURPOSE: Sera from 1356 National Health and Nutrition Examination Survey (NHANES) III participants from seven primary sampling units were tested for serological responses to two Cryptosporidium antigen groups. Intensity of responses was compared by geographic area, age, sex, race/ethnicity, income, and hepatitis A seropositivity. METHODS: Cryptosporidium seropositivity for the 15/17-kDa and the 27-kDa antigen groups were defined by the intensity of the responses. Conditional and unconditional logistic regression was used to identify significant risk factors. RESULTS: Hispanics, blacks, and females had a higher seropositivity. Younger participants and those with higher income had a lower seropositivity. Being hepatitis A seropositive was strongly related to a weak serological response to the 27-kDa antigen group. Family size was unrelated to Cryptosporidium seropositivity. Significantly higher Cryptosporidium seropositivity was observed for three of the seven primary sampling units. CONCLUSIONS: This study found significant geographical differences in the occurrence and the intensity of serological response. Strong serological responses to the 15/17-kDa antigen occurred more commonly in blacks and Hispanics, individuals not having high incomes, and in older age groups.

Is contaminated groundwater an important cause of viral gastroenteritis in the United States?

The large volume of human sewage discharged into the ground has raised concerns about contamination of underground water supplies and possible human health risks. Few groundwater outbreaks reported in the United States, however, have been linked to enteric viruses. Studies on the occurrence of groundwater enteric viruses have detected viruses in groundwater, but many of these studies selected high-risk wells for testing. The results likely overestimated the occurrence of virus contamination in groundwater as well as the resulting public-health risks. This study found only limited evidence for viral contamination of groundwater in the absence of bacterial indicators of sewage contamination. From current studies of virus contamination in groundwater, the authors could not identify a sufficient population with evidence of exposure convincing enough to make an epidemiological investigation feasible and thus were unable to epidemiologically evaluate health risks that may be associated with viral contamination of groundwater. To better estimate the potential health risks, surveys should look at the occurrence of groundwater virus contamination in water that does not have bacterial indicators of sewage contamination and in water that has not been adequately disinfected. These surveys should include groundwater from a wide range of geological conditions.

Outbreaks in drinking-water systems, 1991-1998.

During 1991-1998, 126 outbreaks, 429,021 cases of illness, 653 hospitalizations, and 58 deaths were reported in public and individual water systems in 41 states and three U.S. territories. A bacterial, viral, or protozoan etiology was identified in 41 percent of the outbreaks, and a chemical contaminant was identified in 18 percent. No etiological agent was determined in the remaining outbreaks. Important causes of outbreaks included contamination of untreated groundwater, inadequate disinfection of groundwater, and distribution system deficiencies, especially cross-connections and corrosive water. The responsible pathogen or chemical was identified in water samples collected during 31 percent of the reported outbreaks. Coliform bacteria were detected in water samples collected during the investigation of infectious-disease outbreaks in 83 percent of noncommunity and 46 percent of community water systems, but very few of these systems had exceeded the U.S. Environmental Protection Agency's maximum limit for total coliforms in the 12 months before the outbreak.

Surveillance for waterborne disease outbreaks associated with drinking water---United States, 2007--2008.

PROBLEM/CONDITION: Since 1971, CDC, the Environmental Protection Agency (EPA), and the Council of State and Territorial Epidemiologists have collaborated on the Waterborne Disease and Outbreak Surveillance System (WBDOSS) for collecting and reporting data related to occurrences and causes of waterborne disease outbreaks associated with drinking water. This surveillance system is the primary source of data concerning the scope and health effects of waterborne disease outbreaks in the United States. REPORTING PERIOD: Data presented summarize 48 outbreaks that occurred during January 2007--December 2008 and 70 previously unreported outbreaks. DESCRIPTION OF SYSTEM: WBDOSS includes data on outbreaks associated with drinking water, recreational water, water not intended for drinking (WNID) (excluding recreational water), and water use of unknown intent (WUI). Public health agencies in the states, U.S. territories, localities, and Freely Associated States are primarily responsible for detecting and investigating outbreaks and reporting them voluntarily to CDC by a standard form. Only data on outbreaks associated with drinking water, WNID (excluding recreational water), and WUI are summarized in this report. Outbreaks associated with recreational water are reported separately. RESULTS: A total of 24 states and Puerto Rico reported 48 outbreaks that occurred during 2007--2008. Of these 48 outbreaks, 36 were associated with drinking water, eight with WNID, and four with WUI. The 36 drinking water--associated outbreaks caused illness among at least 4,128 persons and were linked to three deaths. Etiologic agents were identified in 32 (88.9%) of the 36 drinking water--associated outbreaks; 21 (58.3%) outbreaks were associated with bacteria, five (13.9%) with viruses, three (8.3%) with parasites, one (2.8%) with a chemical, one (2.8%) with both bacteria and viruses, and one (2.8%) with both bacteria and parasites. Four outbreaks (11.1%) had unidentified etiologies. Of the 36 drinking water--associated outbreaks, 22 (61.1%) were outbreaks of acute gastrointestinal illness (AGI), 12 (33.3%) were outbreaks of acute respiratory illness (ARI), one (2.8%) was an outbreak associated with skin irritation, and one (2.8%) was an outbreak of hepatitis. All outbreaks of ARI were caused by Legionella spp. A total of 37 deficiencies were identified in the 36 outbreaks associated with drinking water. Of the 37 deficiencies, 22 (59.5%) involved contamination at or in the source water, treatment facility, or distribution system; 13 (35.1%) occurred at points not under the jurisdiction of a water utility; and two (5.4%) had unknown/insufficient deficiency information. Among the 21 outbreaks associated with source water, treatment, or distribution system deficiencies, 13 (61.9%) were associated with untreated ground water, six (28.6%) with treatment deficiencies, one (4.8%) with a distribution system deficiency, and one (4.8%) with both a treatment and a distribution system deficiency. No outbreaks were associated with untreated surface water. Of the 21 outbreaks, 16 (76.2%) occurred in public water systems (drinking water systems under the jurisdiction of EPA regulations and water utility management), and five (23.8%) outbreaks occurred in individual systems (all of which were associated with untreated ground water). Among the 13 outbreaks with deficiencies not under the jurisdiction of a water system, 12 (92.3%) were associated with the growth of Legionella spp. in the drinking water system, and one (7.7%) was associated with a plumbing deficiency. In the two outbreaks with unknown deficiencies, one was associated with a public water supply, and the other was associated with commercially bottled water. The 70 previously unreported outbreaks included 69 Legionella outbreaks during 1973--2000 that were not reportable previously to WBDOSS and one previously unreported outbreak from 2002. INTERPRETATION: 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 a public health problem. The majority of these outbreaks occurred in public water systems that are subject to EPA's new Ground Water Rule (GWR), which requires the majority of community water systems to complete initial sanitary surveys by 2012. The GWR focuses on identification of deficiencies, protection of wells and springs from contamination, and providing disinfection when necessary to protect against bacterial and viral agents. In addition, several drinking water--associated outbreaks that were related to contaminated ground water appeared to occur in systems that were potentially under the influence of surface water. Future efforts to collect data systematically on contributing factors associated with drinking water outbreaks and deficiencies, including identification of ground water under the direct influence of surface water and the criteria used for their classification, would be useful to better assess risks associated with ground water. During 2007--2008, Legionella was the most frequently reported etiology among drinking water--associated outbreaks, following the pattern observed since it was first included in WBDOSS in 2001. However, six (50%) of the 12 drinking water--associated Legionella outbreaks were reported from one state, highlighting the substantial variance in outbreak detection and reporting across states and territories. The addition of published and CDC-investigated legionellosis outbreaks to the WBDOSS database clarifies that Legionella is not a new public health issue. During 2009, Legionella was added to EPA's Contaminant Candidate List for the first time. PUBLIC HEALTH ACTIONS: CDC and EPA use WBDOSS surveillance data to identify the types of etiologic agents, deficiencies, water systems, and sources associated with waterborne disease outbreaks and to evaluate the adequacy of current technologies and practices for providing safe drinking water. Surveillance data also are used to establish research priorities, which can lead to improved water quality regulation development. Approximately two thirds of the outbreaks associated with untreated ground water reported during the 2007--2008 surveillance period occurred in public water systems. When fully implemented, the GWR that was promulgated in 2006 is expected to result in decreases in ground water outbreaks, similar to the decreases observed in surface water outbreaks after enactment of the Surface Water Treatment Rule in 1974 and its subsequent amendments. One third of drinking water--associated outbreaks occurred in building premise plumbing systems outside the jurisdiction of water utility management and EPA regulations; Legionella spp. accounted for >90% of these outbreaks, indicating that greater attention is needed to reduce the risk for legionellosis in building plumbing systems. Finally, a large communitywide drinking water outbreak occurred in 2008 in a public water system associated with a distribution system deficiency, underscoring the importance of maintaining and upgrading drinking water distribution system infrastructure to provide safe water and protect public health.

Surveillance for waterborne disease and outbreaks associated with recreational water use and other aquatic facility-associated health events--United States, 2005-2006.

PROBLEM/CONDITION: Since 1971, CDC, the U.S. Environmental Protection Agency, and the Council of State and Territorial Epidemiologists have collaboratively maintained the Waterborne Disease and Outbreak Surveillance System for collecting and reporting data related to waterborne-disease outbreaks (WBDOs) associated with drinking water. In 1978, WBDOs associated with recreational water (natural and treated water) were added. This system is the primary source of data regarding the scope and effects of disease associated with recreational water in the United States. In addition, data are collected on individual cases of recreational water-associated illnesses and infections and health events occurring at aquatic facilities but not directly related to water exposure. REPORTING PERIOD: Data presented summarize WBDOs and case reports associated with recreational water use that occurred during January 2005--December 2006 and previously unreported disease reports and outbreaks during 1978--2004. DESCRIPTION OF THE SYSTEM: Public health departments in the states, territories, localities, and the Freely Associated States (i.e., the Republic of the Marshall Islands, the Federated States of Micronesia, and the Republic of Palau, formerly parts of the U.S.-administered Trust Territory of the Pacific Islands) have primary responsibility for detecting, investigating, and voluntarily reporting WBDOs to CDC. Although the surveillance system includes data for WBDOs and cases associated with drinking water, recreational water, and water not intended for drinking, only cases and outbreaks associated with recreational water and health events at aquatic facilities are summarized in this report. RESULTS: During 2005--2006, a total of 78 WBDOs associated with recreational water were reported by 31 states. Illness occurred in 4,412 persons, resulting in 116 hospitalizations and five deaths. The median outbreak size was 13 persons (range: 2--2,307 persons). Of the 78 WBDOs, 48 (61.5%) were outbreaks of gastroenteritis that resulted from infectious agents or chemicals; 11 (14.1%) were outbreaks of acute respiratory illness; and 11 (14.1%) were outbreaks of dermatitis or other skin conditions. The remaining eight were outbreaks of leptospirosis (n = two), primary amebic meningoencephalitis (n = one), and mixed or other illnesses (n = five). WBDOs associated with gastroenteritis resulted in 4,015 (91.0%) of 4,412 illnesses. Fifty-eight (74.4%) WBDOs occurred at treated water venues, resulting in 4,167 (94.4%) cases of illness. The etiologic agent was confirmed in 62 (79.5%) of the 78 WBDOs, suspected in 12 (15.4%), and unidentified in four (5.1%). Thirty-four (43.6%) WBDOs had a parasitic etiology; 22 (28.2%), bacterial; four (5.1%), viral; and two (2.6%), chemical or toxin. Among the 48 gastroenteritis outbreaks, Cryptosporidium was confirmed as the causal agent in 31 (64.6%), and all except two of these outbreaks occurred in treated water venues where Cryptosporidium caused 82.9% (29/35) of the gastroenteritis outbreaks. Case reports associated with recreational water exposure that were discussed and analyzed separately from outbreaks include three fatal Naegleria cases and 189 Vibrio illnesses reported to the Cholera and Other Vibrio Illness Surveillance System. For Vibrio reporting, the most commonly reported species were Vibrio vulnificus, V. alginolyticus, and V. parahaemolyticus. V. vulnificus illnesses associated with recreational water exposure had the highest Vibrio illness hospitalization (77.6%) and mortality (22.4%) rates. In addition, 32 aquatic facility-related health events not associated with recreational water use (e.g., pool chemical mixing accidents) that occurred during 1983--2006 were received from New York. These events, which caused illness in 364 persons, are included in this report but analyzed separately. INTERPRETATIONS: The number of WBDOs summarized in this report and the trends in recreational water-associated disease and outbreaks demonstrate a substantial increase in number of reports from previous years. Outbreaks, especially the largest ones, occurred more frequently in the summer at treated water venues and caused gastrointestinal illness. Deficiencies leading to WBDOs included problems with water-quality, venue design, usage, and maintenance. Case reports of illness associated with recreational water use expand our understanding of the scope of waterborne illness by further underscoring the contribution of less well-recognized swimming venues (e.g., oceans) and illness (e.g., nongastrointestinal illness). Aquatic facilities are also a focus for injuries involving chemicals or equipment used routinely in the operation of swimming venues, thus illustrating the lack of training of some aquatics staff. PUBLIC HEALTH ACTIONS: CDC uses WBDO surveillance data to 1) identify the etiologic agents, types of aquatic venues, water-treatment systems, and deficiencies associated with outbreaks and case reports; 2) evaluate the adequacy of efforts (i.e., regulations and public awareness activities) to provide safe recreational water; 3) expand the scope of understanding about waterborne disease and health events associated with swimming and aquatics facilities; and 4) establish public health prevention priorities, data, and messaging that might lead to improved regulations, guidelines, and prevention measures at the local, state, and federal levels.

Surveillance for waterborne disease and outbreaks associated with drinking water and water not intended for drinking--United States, 2005-2006.

PROBLEM/CONDITION: Since 1971, CDC, the U.S. Environmental Protection Agency (EPA), and the Council of State and Territorial Epidemiologists have maintained a collaborative Waterborne Disease and Outbreak Surveillance System (WBDOSS) for collecting and reporting data related to occurrences and causes of waterborne-disease outbreaks (WBDOs) and cases of waterborne disease. This surveillance system is the primary source of data concerning the scope and effects of waterborne disease in the United States. REPORTING PERIOD: Data presented summarize 28 WBDOs that occurred during January 2005--December 2006 and four previously unreported WBDOs that occurred during 1979--2002. DESCRIPTION OF SYSTEM: The surveillance system includes data on WBDOs associated with recreational water, drinking water, water not intended for drinking (WNID) (excluding recreational water), and water use of unknown intent. Public health departments in the states, territories, localities, and Freely Associated States (FAS) (i.e., the Republic of the Marshall Islands, the Federated States of Micronesia, and the Republic of Palau, formerly parts of the U.S.-administered Trust Territory of the Pacific Islands) are primarily responsible for detecting and investigating WBDOs and voluntarily reporting them to CDC by a standard form. Only cases and outbreaks associated with drinking water, WNID (excluding recreational water), and water of unknown intent (WUI) are summarized in this report. Cases and outbreaks associated with recreational water are reported in a separate Surveillance Summary. RESULTS: Fourteen states reported 28 WBDOs that occurred during 2005--2006: a total of 20 were associated with drinking water, six were associated with WNID, and two were associated with WUI. The 20 drinking water-associated WBDOs caused illness among an estimated 612 persons and were linked to four deaths. Etiologic agents were identified in 18 (90.0%) of the drinking water-associated WBDOs. Among the 18 WBDOs with identified pathogens, 12 (66.7%) were associated with bacteria, three (16.7%) with viruses, two (11.1%) with parasites, and one (5.6%) mixed WBDO with both bacteria and viruses. In both WBDOs where the etiology was not determined, norovirus was the suspected etiology. Of the 20 drinking water WBDOs, 10 (50) were outbreaks of acute respiratory illness (ARI), nine (45%) were outbreaks of acute gastrointestinal illness (AGI), and one (5.0%) was an outbreak of hepatitis. All WBDOs of ARI were caused by Legionella, and this is the first reporting period in which the proportion of ARI WBDOs has surpassed that of AGI WBDOs since the reporting of Legionella WBDOs was initiated in 2001. A total of 23 deficiencies were cited in the 20 WBDOs associated with drinking water: 12 (52.2%) deficiencies fell under the classification NWU/POU (deficiencies occurred at points not under the jurisdiction of a water utility or at the point-of-use), 10 (43.5%) deficiencies fell under the classification SWTDs (contamination at or in the source water, treatment facility, or distribution system), and for one (4.3%) deficiency, classification was unknown. Among the 12 NWU/POU deficiencies, 10 (83.3%) involved Legionella spp. in the drinking water system. The most frequently cited SWTD deficiencies were associated with a treatment deficiency (n = four [40.0%]) and untreated ground water (n = four [40.0%]). Three of the four WBDOs with treatment deficiencies used ground water sources. INTERPRETATION: Approximately half (52.2%) of the drinking water deficiencies occurred outside the jurisdiction of a water utility. The majority of these WBDOs were associated with Legionella spp, which suggests that increased attention should be targeted towards reducing illness risks associated with Legionella spp. Nearly all of WBDOs associated with SWTD deficiencies occurred in systems using ground water. EPA's new Ground Water Rule might prevent similar outbreaks in the future in public water systems. PUBLIC HEALTH ACTIONS: CDC and EPA use surveillance data to identify the types of water systems, deficiencies, and etiologic agents associated with WBDOs and to evaluate the adequacy of current technologies and practices for providing safe drinking water. Surveillance data also are used to establish research priorities, which can lead to improved water-quality regulation development. The majority of drinking water deficiencies are now associated with contamination at points outside the jurisdiction of public water systems (e.g., regrowth of Legionella spp. in hot water systems) and water contamination that might not be regulated by EPA (e.g., contamination of tap water at the POU). Improved education of consumers and plumbers might help address these risk factors.

Review of epidemiological studies on drinking water hardness and cardiovascular diseases.

BACKGROUND: Major risk factors do not entirely explain the worldwide variability of morbidity and mortality due to cardiovascular disease. Environmental exposures, including drinking water minerals may affect cardiovascular disease risks. METHOD: We conducted a qualitative review of the epidemiological studies of cardiovascular disease and drinking water hardness and calcium and magnesium levels. RESULTS: Many but not all ecological studies found an inverse (i.e., protective) association between cardiovascular disease mortality and water hardness, calcium, or magnesium levels; but results are not consistent. Some case-control studies and one cohort study found either a reduced cardiovascular disease mortality risk with increased drinking water magnesium levels or an increased risk with low magnesium levels. However, the analytical studies provide little evidence that cardiovascular risks are associated with drinking water hardness or calcium levels. CONCLUSION: Information from epidemiological and other studies supports the hypothesis that a low intake of magnesium may increase the risk of dying from, and possibly developing, cardiovascular disease or stroke. Thus, not removing magnesium from drinking water, or in certain situations increasing the magnesium intake from water, may be beneficial, especially for populations with an insufficient dietary intake of the mineral.

Surveillance for waterborne disease and outbreaks associated with recreational water--United States, 2003-2004.

PROBLEM/CONDITION: Since 1971, CDC, the U.S. Environmental Protection Agency, and the Council of State and Territorial Epidemiologists have collaboratively maintained the Waterborne Disease and Outbreak Surveillance System for collecting and reporting waterborne disease and outbreak (WBDO)-related data. In 1978, WBDOs associated with recreational water (natural and treated water) were added. This system is the primary source of data regarding the scope and effects of WBDOs in the United States. REPORTING PERIOD: Data presented summarize WBDOs associated with recreational water that occurred during January 2003-December 2004 and one previously unreported outbreak from 2002. DESCRIPTION OF THE SYSTEM: Public health departments in the states, territories, localities, and the Freely Associated States (i.e., the Republic of the Marshall Islands, the Federated States of Micronesia, and the Republic of Palau, formerly parts of the U.S.-administered Trust Territory of the Pacific Islands) have primary responsibility for detecting, investigating, and voluntarily reporting WBDOs to CDC. Although the surveillance system includes data for WBDOs associated with drinking water, recreational water, and water not intended for drinking, only cases and outbreaks associated with recreational water are summarized in this report. RESULTS: During 2003-2004, a total 62 WBDOs associated with recreational water were reported by 26 states and Guam. Illness occurred in 2,698 persons, resulting in 58 hospitalizations and one death. The median outbreak size was 14 persons (range: 1-617 persons). Of the 62 WBDOs, 30 (48.4%) were outbreaks of gastroenteritis that resulted from infectious agents, chemicals, or toxins; 13 (21.0%) were outbreaks of dermatitis; and seven (11.3%) were outbreaks of acute respiratory illness (ARI). The remaining 12 WBDOs resulted in primary amebic meningoencephalitis (n = one), meningitis (n = one), leptospirosis (n = one), otitis externa (n = one), and mixed illnesses (n = eight). WBDOs associated with gastroenteritis resulted in 1,945 (72.1%) of 2,698 illnesses. Forty-three (69.4%) WBDOs occurred at treated water venues, resulting in 2,446 (90.7%) cases of illness. The etiologic agent was confirmed in 44 (71.0%) of the 62 WBDOs, suspected in 15 (24.2%), and unidentified in three (4.8%). Twenty (32.3%) WBDOs had a bacterial etiology; 15 (24.2%), parasitic; six (9.7%), viral; and three (4.8%), chemical or toxin. Among the 30 gastroenteritis outbreaks, Cryptosporidium was confirmed as the causal agent in 11 (36.7%), and all except one of these outbreaks occurred in treated water venues where Cryptosporidium caused 55.6% (10/18) of the gastroenteritis outbreaks. In this report, 142 Vibrio illnesses (reported to the Cholera and Other Vibrio Illness Surveillance System) that were associated with recreational water exposure were analyzed separately. The most commonly reported species were Vibrio vulnificus, V. alginolyticus, and V. parahaemolyticus. V. vulnificus illnesses associated with recreational water exposure had the highest Vibrio illness hospitalization (87.2%) and mortality (12.8%) rates. INTERPRETATION: The number of WBDOs summarized in this report and the trends in recreational water-associated disease and outbreaks are consistent with previous years. Outbreaks, especially the largest ones, are most likely to be associated with summer months, treated water venues, and gastrointestinal illness. Approximately 60% of illnesses reported for 2003-2004 were associated with the seven largest outbreaks (>100 cases). Deficiencies leading to WBDOs included problems with water quality, venue design, usage, and maintenance. PUBLIC HEALTH ACTIONS: CDC uses WBDO surveillance data to 1) identify the etiologic agents, types of aquatic venues, water-treatment systems, and deficiencies associated with outbreaks; 2) evaluate the adequacy of efforts (i.e., regulations and public awareness activities) to provide safe recreational water; and 3) establish public health prevention priorities that might lead to improved regulations and prevention measures at the local, state, and federal levels.

Surveillance for waterborne disease and outbreaks associated with drinking water and water not intended for drinking--United States, 2003-2004.

PROBLEM/CONDITION: Since 1971, CDC, the U.S. Environmental Protection Agency (EPA), and the Council of State and Territorial Epidemiologists have maintained a collaborative Waterborne Disease and Outbreaks Surveillance System for collecting and reporting data related to occurrences and causes of waterborne disease and outbreaks (WBDOs). This surveillance system is the primary source of data concerning the scope and effects of WBDOs in the United States. REPORTING PERIOD: Data presented summarize 36 WBDOs that occurred during January 2003-December 2004 and nine previously unreported WBDOs that occurred during 1982-2002. DESCRIPTION OF SYSTEM: The surveillance system includes data on WBDOs associated with drinking water, water not intended for drinking (excluding recreational water), and water of unknown intent. Public health departments in the states, territories, localities, and Freely Associated States (i.e., the Republic of the Marshall Islands, the Federated States of Micronesia, and the Republic of Palau, formerly parts of the U.S.-administered Trust Territory of the Pacific Islands) are primarily responsible for detecting and investigating WBDOs and voluntarily reporting them to CDC by using a standard form. RESULTS: During 2003-2004, a total of 36 WBDOs were reported by 19 states; 30 were associated with drinking water, three were associated with water not intended for drinking, and three were associated with water of unknown intent. The 30 drinking water-associated WBDOs caused illness among an estimated 2,760 persons and were linked to four deaths. Etiologic agents were identified in 25 (83.3%) of these WBDOs: 17 (68.0%) involved pathogens (i.e., 13 bacterial, one parasitic, one viral, one mixed bacterial/parasitic, and one mixed bacterial/parasitic/viral), and eight (32.0%) involved chemical/toxin poisonings. Gastroenteritis represented 67.7% of the illness related to drinking water-associated WBDOs; acute respiratory illness represented 25.8%, and dermatitis represented 6.5%. The classification of deficiencies contributing to WBDOs has been revised to reflect the categories of concerns associated with contamination at or in the source water, treatment facility, or distribution system (SWTD) that are under the jurisdiction of water utilities, versus those at points not under the jurisdiction of a water utility or at the point of water use (NWU/POU), which includes commercially bottled water. A total of 33 deficiencies were cited in the 30 WBDOs associated with drinking water: 17 (51.5%) NWU/POU, 14 (42.4%) SWTD, and two (6.1%) unknown. The most frequently cited NWU/POU deficiencies involved Legionella spp. in the drinking water system (n = eight [47.1%]). The most frequently cited SWTD deficiencies were associated with distribution system contamination (n = six [42.9%]). Contaminated ground water was a contributing factor in seven times as many WBDOs (n = seven) as contaminated surface water (n = one). INTERPRETATION: Approximately half (51.5%) of the drinking water deficiencies occurred outside the jurisdiction of a water utility in situations not currently regulated by EPA. The majority of the WBDOs in which deficiencies were not regulated by EPA were associated with Legionella spp. or chemicals/toxins. Problems in the distribution system were the most commonly identified deficiencies under the jurisdiction of a water utility, underscoring the importance of preventing contamination after water treatment. The substantial proportion of WBDOs involving contaminated ground water provides support for the Ground Water Rule (finalized in October 2006), which specifies when corrective action is required for public ground water systems. PUBLIC HEALTH ACTIONS: CDC and EPA use surveillance data to identify the types of water systems, deficiencies, and etiologic agents associated with WBDOs and to evaluate the adequacy of current technologies and practices for providing safe drinking water. Surveillance data also are used to establish research priorities, which can lead to improved water-quality regulation development. The growing proportion of drinking water deficiencies that are not addressed by current EPA rules emphasizes the need to address risk factors for water contamination in the distribution system and at points not under the jurisdiction of water utilities.