Serological responses to Cryptosporidium-specific antigens in Czech populations with different water sources.

Serological responses to Cryptosporidium-specific antigens (15/17 and 27 kDa) were compared among populations in four areas of the Czech Republic that use drinking water from clearly defined sources: (1) wells in a fractured sandstone aquifer, (2) riverbank infiltration, or (3) two different filtered and chlorinated surface waters. Among persons surveyed in the area with riverbank-infiltration water, 33% had a strong serological response to the 15/17-kDa antigen group whereas, in the other three areas, over 72% of persons had a strong response. These response differences suggest that Cryptosporidium exposures and infection were lower in the area with bank infiltration. The large percentage of the study population with a strong serological response to both antigens suggests high levels of previous infections that may have resulted in protective immunity for cryptosporidiosis. This may be one reason why no waterborne cryptosporidiosis outbreaks and few cases of cryptosporidiosis have been reported in the Czech Republic.

Serological responses to Cryptosporidium antigens among users of surface- vs. ground-water sources.

Cryptosporidium oocysts are commonly detected in surface-derived drinking water. However, the public health significance of these findings is unclear. This study compared serological responses to two Cryptosporidium antigen groups for blood donors and college students using chlorinated and filtered river water vs. ground-water sources. The surface water received agricultural and domestic sewage discharges upstream. Participants from the surface-water city had a higher relative prevalence (RP) of a serological response to the 15/17-kDa antigen group (72.3 vs. 52.4%, RP = 1.36, P < 0.001) and to the 27-kDa antigen group (82.6 vs. 72.5%, RP = 1.14, P < 0.02). Multivariate logistic regression analysis found that the people with a shorter duration of residence or drinking bottled water also had a lower seropositivity for each marker. Use of private wells was associated with a higher prevalence of response to the 15/17-kDa markers. Seroconversion to the 15/17-kDa antigen group was more common in the residents of the city using surface water. These findings are consistent with an increased risk of Cryptosporidium infection for users of surface-derived drinking water compared with users of municipal ground-water-derived drinking water. Users of private well water may also have an increased risk of infection.

Possible information bias in a waterborne outbreak investigation.

Although an investigation of a cryptosporidiosis outbreak in 1994 in Clark County, Nevada, concluded that illness was associated with consumption of municipal water, no water treatment deficiencies or breakdowns and no water quality changes were discovered during the investigation. We evaluated the strength of the evidence for waterborne transmission and conducted a sensitivity analysis to define the limitations of the epidemiological data. Our analyses suggest a spurious inference of waterborne transmission might be due to differential misclassification bias. If exposure and disease status were incorrectly classified for a relatively small number of study participants, findings of the investigation would be interpreted differently. We offer this example to illustrate the importance of assessing the stability of a relative risk estimate and effect of possible biases during an outbreak investigation.

Improving waterborne disease outbreak investigations.

This article is a summary of discussions held and recommendations made at a workshop for the investigation of waterborne disease outbreaks in Chapel Hill, North Carolina, December 7-8, 1998. Suspected waterborne outbreaks in the United States are primarily investigated by state and local public health officials who may infrequently conduct enteric disease outbreak investigations. Thus, it is important that officials have a formal plan to ensure that epidemiological studies are methodologically sound and that effective collaboration occurs among the epidemiologists, scientists, and engineers who will conduct the investigations. Laboratory support to analyze water samples and clinical specimens should be arranged well in advance of when services may be needed. Enhanced surveillance activities can help officials recognize additional outbreaks and initiate investigations in a timely manner. Epidemiologists should pay more attention early in the investigation to study design, questionnaire development, and sources of bias, especially recall bias, that may affect the interpretation of observed associations. Improved investigations can increase our knowledge about important etiological agents, water systems deficiencies, and sources of water contamination so that waterborne outbreaks can be more effectively prevented.

Paired city cryptosporidium serosurvey in the southwest USA.

In 1996, serological responses to two Cryptosporidium antigens were determined for 200 Las Vegas (LV), Nevada, and 200 Albuquerque, New Mexico, blood donors to evaluate associations between endemic infections, water exposures, and other risk factors. LV uses chlorinated filtered drinking water from Lake Mead while Albuquerque uses chlorinated ground water. The intensity of serological response to both markers was higher for older donors (P < 0.05). donors who washed food with bottled water (P < 0.05) and donors from LV (P < 0.05). A decreased serological response was not associated with bottled water consumption, nor was an increased response associated with self-reported cryptosporidiosis-like illness or residence in LV at the time of a cryptosporidiosis outbreak 2 years earlier. Although these findings suggest the serological response may be associated with type of tap water and certain foods, additional research is needed to clarifythe role of both food and drinking water in endemic Cryptosporidium infection.

A serological survey of college students for antibody to Cryptosporidium before and after the introduction of a new water filtration plant.

In April 1997, a large city in the northeastern United States changed their drinking water treatment practices. The city, which previously provided only chlorination for their surface water sources added filtration in addition to chlorination. To assess whether Cryptosporidium infections rates declined following filtration, we tested serological responses to 15/17-kDa and 27-kDa Cryptosporidium antigens among 107 community college students 1 month before and 225 students 5 months after filtration. Results suggest that levels of Cryptosporidium infections did not decline following water filtration. However, seasonal changes in other exposures may have confounded the findings. Swimming in a lake, stream or public pool and drinking untreated water from a lake or stream predicted a more intense response to one or both markers. Residence in the city, not drinking city tap water or drinking bottled water, gender, travel or exposure to pets, young pets, diapers or a household child in day care were not found to be predictive of more or less intense serological responses for either the 15/17-kDa and 27-kDa antigen.

Serological evidence of Cryptosporidium infections in southern Europe.

Although cryptosporidiosis outbreaks have been frequently reported in the United States, Canada and the United Kingdom, few outbreaks have been reported on the European continent. The reasons for this are unclear. To ascertain whether a European population has been previously exposed to Cryptosporidium, we conducted a survey of 100 resident blood donors in a northern Italian city for IgG serological response to two oocyst antigen groups. A serological response to the 15/17-kDa antigen group was detected in 83% of blood donors and response to the 27-kDa antigen group in 62%. Donors who traveled outside of Italy during the prior 12 months were less likely to have had a response to the 15/17-kDa antigen group (p < 0.04) and to have a less intense response (p < 0.05). Older age was predictive of a more intense response to each antigen group (p < 0.01). The fraction of Italian blood donors with a serological response to either antigen group was higher than in four United States blood donor populations, with differences more pronounced for response to the 15/17-kDa antigen group (p < 0.01). A lower fraction of Italian donors had a serological response to either antigen group than persons tested at the time of a cryptosporidiosis outbreak in the United States or blood donors tested six months after that outbreak (p < 0.05). Since the presence of serological responses to these antigen groups predicts a reduced risk of cryptosporidiosis, the high prevalence of serological responses in these Italian blood donors may explain the infrequent occurrences of clinically detectable cryptosporidiosis in this city.

Surveillance for waterborne-disease outbreaks--United States, 1997-1998.

PROBLEM/CONDITION: Since 1971, CDC and the U.S. Environmental Protection Agency (EPA) have maintained a collaborative surveillance system for collecting and periodically reporting data relating to occurrences and causes of waterborne-disease outbreaks (WBDOs). REPORTING PERIOD COVERED: This summary includes data from January 1997 through December 1998 and a previously unreported outbreak in 1996. DESCRIPTION OF THE SYSTEM: The surveillance system includes data regarding 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. RESULTS: During 1997-1998, a total of 13 states reported 17 outbreaks associated with drinking water. These outbreaks caused an estimated 2,038 persons to become ill. No deaths were reported. The microbe or chemical that caused the outbreak was identified for 12 (70.6%) of the 17 outbreaks; 15 (88.2%) were linked to groundwater sources. Thirty-two outbreaks from 18 states were attributed to recreational water exposure and affected an estimated 2,128 persons. Eighteen (56.3%) of the 32 were outbreaks of gastroenteritis, and 4 (12.5%) were single cases of primary amebic meningoencephalitis caused by Naegleria fowleri, all of which were fatal. The etiologic agent was identified for 29 (90.6%) of the 32 outbreaks, with one death associated with an Escherichia coli O157:H7 outbreak. Ten (55.6%) of the 18 gastroenteritis outbreaks were associated with treated pools or ornamental fountains. Of the eight outbreaks of dermatitis, seven (87.5%) were associated with hot tubs, pools, or springs. INTERPRETATION: Drinking water outbreaks associated with surface water decreased from 31.8% during 1995-1996 to 11.8% during 1997-1998. This reduction could be caused by efforts by the drinking water industry (e.g., Partnership for Safe Water), efforts by public health officials to improve drinking water quality, and improved water treatment after the implementation of EPA's Surface Water Treatment Rule. In contrast, the proportion of outbreaks associated with systems supplied by a groundwater source increased from 59.1% (i.e., 13) during 1995-1996 to 88.2% (i.e., 15) during 1997-1998. Outbreaks caused by parasites increased for both drinking and recreational water. All outbreaks of gastroenteritis attributed to parasites in recreational water were caused by Cryptosporidium, 90% occurred in treated water venues (e.g., swimming pools and decorative fountains), and fecal accidents were usually suspected. The data in this surveillance summary probably underestimate the true incidence of WBDOs because not all WBDOs are recognized, investigated, and reported to CDC or EPA. ACTIONS TAKEN: To estimate the national prevalence of waterborne disease associated with drinking water, CDC and EPA are conducting a series of epidemiologic studies to better quantify the level of waterborne disease associated with drinking water in nonoutbreak conditions. The Information Collection Rule implemented by EPA in collaboration with the drinking water industry helped quantifythe level of pathogens in surface water. Efforts by CDC to address recreational water outbreaks have included meetings with the recreational water industry, focus groups to educate parents on prevention of waterborne disease transmission in recreational water settings, and publications with guidelines for parents and pool operators.

Serological analysis of a cryptosporidiosis epidemic.

BACKGROUND: A cryptosporidiosis epidemic occurred among residents and visitors to Collingwood, Ontario, during March 1996. Fifty-five per cent of 36 confirmed cases were Collingwood visitors and 57% of Collingwood resident cases were under 10 years of age. The low level of reported diarrhoeal illness among adult Collingwood residents caused government officials and physicians to question whether an epidemic had occurred in Collingwood. METHODS: To better evaluate the extent of the epidemic, anonymous surplus sera from 89 adult Collingwood residents, collected for routine tests prior to, during and after the epidemic, and from 80 adult Toronto residents were tested using a Western blot assay for IgG antibody response to two Cryptosporidium antigen groups (15/17-kDa and 27-kDa). RESULTS: For sera collected from 1 January 1996 to 17 June 1996, a higher fraction of Collingwood residents had a detectable serological response (P < 0.002) and the mean intensity of serological responses was higher for Collingwood than Toronto residents (P < 0.001). The mean intensity of serological responses for Collingwood residents was higher in specimens drawn during the 8 weeks following the initial case reports compared to those drawn before or after this period (15/17-kDa, P < 0.02; 27-kDa, P < 0.10). CONCLUSIONS: These elevated serological responses indicate that Cryptosporidium infections among Collingwood residents likely occurred more commonly than illness reports suggested, consistent with a community-wide cryptosporidiosis epidemic. Similar studies should be considered in future suspected cryptosporidiosis epidemic investigations.

Increasing hospitalization and death possibly due to Clostridium difficile diarrheal disease.

This study calculated yearly estimated national hospital discharge (1985 to 1994) and age-adjusted death rates (1980 to 1992) due to bacterial, viral, protozoal, and ill-defined enteric pathogens. Infant and young child hospitalization (but not death) rates in each category increased more than 50% during 1990 to 1994. Age-adjusted death and hospitalization rates due to enteric bacterial infections and hospitalizations due to enteric viral infections have increased since 1988. The increases in hospitalization and death rates from enteric bacterial infections were due to a more than eightfold increase in rates for specified enteric bacterial infections that were uncoded during this period (ICD9 00849). To identify bacterial agents responsible for most of these infections, hospital discharges and outpatient claims (coded with more detail after 1992) were examined for New Mexico's Lovelace Health Systems for 1993 to 1996. Of diseases due to uncoded enteric pathogens, 73% were due to Clostridium difficile infection. Also, 88% of Washington State death certificates (1985 to 1996) coded to unspecified enteric pathogen infections (ICD0084) listed C. difficile infection.

Surveillance for waterborne-disease outbreaks--United States, 1995-1996.

PROBLEM/CONDITION: Since 1971, CDC and the U.S. Environmental Protection Agency have maintained a collaborative surveillance system for collecting and periodically reporting data that relate to occurrences and causes of waterborne-disease outbreaks (WBDOs). REPORTING PERIOD COVERED: This summary includes data for January 1995 through December 1996 and previously unreported outbreaks in 1994. DESCRIPTION OF THE SYSTEM: The surveillance system includes data about outbreaks associated with drinking water and recreational water. State, territorial, and local public health departments are primarily responsible for detecting and investigating WBDOs and for voluntarily reporting them to CDC on a standard form. RESULTS: For the period 1995-1996, 13 states reported a total of 22 outbreaks associated with drinking water. These outbreaks caused an estimated total of 2,567 persons to become ill. No deaths were reported. The microbe or chemical that caused the outbreak was identified for 14 (63.6%) of the 22 outbreaks. Giardia lamblia and Shigella sonnei each caused two (9.1%) of the 22 outbreaks; Escherichia coli O157:H7, Plesiomonas shigelloides, and a small round structured virus were implicated for one outbreak (4.5%) each. One of the two outbreaks of giardiasis involved the largest number of cases, with an estimated 1,449 ill persons. Seven outbreaks (31.8% of 22) of chemical poisoning, which involved a total of 90 persons, were reported. Copper and nitrite were associated with two outbreaks (9.1% of 22) each and sodium hydroxide, chlorine, and concentrated liquid soap with one outbreak (4.5%) each. Eleven (50.0%) of the 22 outbreaks were linked to well water, eight in noncommunity and three in community systems. Only three of the 10 outbreaks associated with community water systems were caused by problems at water treatment plants; the other seven resulted from problems in the water distribution systems and plumbing of individual facilities (e.g., a restaurant). Six of the seven outbreaks were associated with chemical contamination of the drinking water; the seventh outbreak was attributed to a small round structured virus. Four of the seven outbreaks occurred because of backflow or backsiphonage through a cross-connection, and two occurred because of high levels of copper that leached into water after the installation of new plumbing. For three of the four outbreaks caused by contamination from a cross-connection, an improperly installed vacuum breaker or a faulty backflow prevention device was identified; no protection against backsiphonage was found for the fourth outbreak. Thirty-seven outbreaks from 17 states were attributed to recreational water exposure and affected an estimated 9,129 persons, including 8,449 persons in two large outbreaks of cryptosporidiosis. Twenty-two (59.5%) of these 37 were outbreaks of gastroenteritis; nine (24.3%) were outbreaks of dermatitis; and six (16.2%) were single cases of primary amebic meningoencephalitis caused by Naegleria fowleri, all of which were fatal. The etiologic agent was identified for 33 (89.2%) of the 37 outbreaks. Six (27.3%) of the 22 outbreaks of gastroenteritis were caused by Cryptosporidium parvum and six (27.3%) by E. coli O157:H7. All of the latter were associated with unchlorinated water (i.e., in lakes) or inadequately chlorinated water (i.e., in a pool). Thirteen (59.1%) of these 22 outbreaks were associated with lake water, eight (36.4%) with swimming or wading pools, and one(4.5%) with a hot spring. Of the nine outbreaks of dermatitis, seven (77.8%) were outbreaks of Pseudomonas dermatitis associated with hot tubs, and two (22.2%) were lake-associated outbreaks of swimmer's itch caused by Schistosoma species. INTERPRETATION: WBDOs caused by E. coli O157:H7 were reported more frequently than in previous years and were associated primarily with recreational lake water. This finding suggests the need for better monitoring of water quality and identification of sources of

Surveillance for waterborne-disease outbreaks--United States, 1993-1994.

PROBLEM/CONDITION: Since 1971, CDC and the U.S. Environmental Protection Agency have maintained a collaborative surveillance system for collecting and periodically reporting data that relate to occurrences and causes of waterborne-disease outbreaks (WBDOs). REPORTING PERIOD COVERED: This summary includes data for January 1993 through December 1994 and for previously unreported outbreaks in 1992. DESCRIPTION OF THE SYSTEM: The surveillance system includes data about outbreaks associated with water intended for drinking (i.e., drinking water) and those associated with 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. RESULTS: For the 2-year period 1993-1994, 17 states and one territory reported a total of 30 outbreaks associated with drinking water. These outbreaks caused an estimated 405,366 persons to become ill, including 403,000 from an outbreak of cryptosporidiosis in Milwaukee, the largest WBDO ever documented in the United States, and 2,366 from the other 29 outbreaks. No etiologic agent was identified for five (16.7%) of the 30 outbreaks. The protozoan parasites Giardia lamblia and Cryptosporidium parvum caused 10 (40.0%) of the 25 outbreaks for which the etiologic agent was identified. Two outbreaks of cryptosporidiosis occurred in large metropolitan areas (i.e., Milwaukee and Las Vegas/Clark County) and were associated with deaths among immunocompromised persons. The waterborne nature of these two outbreaks was not recognized until at least 2 weeks after the onset of the Milwaukee outbreak and until after the end of the Las Vegas outbreak. Campylobacter jejuni was implicated for three outbreaks and the following pathogens for one outbreak each: Shigella sonnei, Shigella flexneri, non-O1 Vibrio cholerae (in a U.S. territory; the vehicle was commercially bottled water), and Salmonella serotype Typhimurium (the outbreak was associated with seven deaths). Eight outbreaks of chemical poisoning were reported: three were caused by lead (one case each), two by fluoride, two by nitrate and one by copper. Twenty (66.7%) of the 30 outbreaks were associated with a well-water source. Fourteen states reported a total of 26 outbreaks associated with recreational water, in which an estimated 1,714 persons became ill. Fourteen (53.8%) of these 26 were outbreaks of gastroenteritis. The etiologic agent in each of these 14 outbreaks was identified; 10 (71.4%) were caused by G. lamblia or C. parvum. Six of these 10 were associated with chlorinated, filtered pool water, and three with lake water. One of the latter was the first reported outbreak of cryptosporidiosis associated with the recreational use of lake water. Four outbreaks of lake water-associated bacterial gastroenteritis were reported, two caused by S. sonnei, one by S. flexneri, and one by Escherichia coli O157:H7. Nine outbreaks of hot tub- whirlpool-, or swimming pool-associated pseudomonas dermatitis were reported. Two outbreaks of swimming pool-associated dermatitis had a suspected chemical etiology. The child who had the one reported case of primary amebic meningoencephalitis, caused by infection with Naegleria fowleri, died. INTERPRETATION: The number of WBDOs reported annually has been similar for each year during 1987-1994, except for an increase in 1992. Protozoan parasites, especially C. parvum and G. lamblia, remain important etiologic agents of WBDOs. The outbreaks of cryptosporidiosis in Milwaukee and Las Vegas demonstrate that WBDOs can occur in large metropolitan areas. Surveillance methods are needed that expedite the detection of WBDOs and the institution of preventive measures (e.g., boil-water advisories). ACTIONS TAKEN: Surveillance data that identify the types of water systems, their deficiencies, and the etiologic agents associated with outbreaks are used to evaluate the adequacy of current technologies for prov

Surveillance for waterborne disease outbreaks--United States, 1991-1992.

PROBLEM/CONDITION: Since 1971, CDC and the U.S. Environmental Protection Agency have maintained a collaborative surveillance program for collection and periodic reporting of data on the occurrence and causes of waterborne disease outbreaks. REPORTING PERIOD COVERED: January 1991 through December 1992. DESCRIPTION OF SYSTEM: The surveillance system includes data about outbreaks associated with water intended for drinking and also about those associated with recreational water. State and local public health departments are the agencies with primary responsibility for the detection and investigation of outbreaks. State and territorial health departments report these outbreaks to CDC on a standard form. RESULTS: For the 2-year period 1991-1992, 17 states and territories reported 34 outbreaks associated with water intended for drinking. The outbreaks caused an estimated 17,464 persons to become ill. A protozoal parasite (Giardia lamblia or Cryptosporidium) was identified as the etiologic agent for seven of the 11 outbreaks for which an agent was determined. Five (71%) of the outbreaks caused by protozoa were associated with a surface-influenced groundwater source. One outbreak of cryptosporidiosis was associated with filtered and chlorinated surface water. Shigella sonnei and hepatitis A virus were implicated in one outbreak each; both were linked to consumption of contaminated well water. Two outbreaks due to acute chemical poisoning were reported; one had an associated fatality. No etiology was established for 23 (68%) of the 34 outbreaks, including the largest one reported during this period, in which an estimated 9,847 persons using a filtered surface water supply developed gastroenteritis. Most (76%) of the 34 outbreaks were associated with a well water source. Twenty-one states reported 39 outbreaks associated with recreational water, in which an estimated 1,825 persons became ill. The most frequently reported illness was hot tub- or whirlpool-associated Pseudomonas dermatitis (12 outbreaks). Of 11 outbreaks of swimming-associated gastroenteritis, six were caused by Giardia or Cryptosporidium, including three outbreaks associated with chlorinated, filtered pool water. The first reported outbreak of Escherichia coli O157:H7 infection associated with recreational exposure occurred during this period. Primary amebic meningoencephalitis, caused by Naegleria fowleri infection, resulted in six deaths. INTERPRETATION: The number of waterborne disease outbreaks reported per year has not changed substantially in the past 5 years. However, etiologic agents only recently associated with waterborne disease, such as E. coli O157:H7 and Cryptosporidium, are being reported more frequently and from new settings. Water quality data for outbreaks during the period 1991-1992 indicate that available water disinfection technology is not always in place or used reliably.(ABSTRACT TRUNCATED AT 400 WORDS)

Health risks from contaminated water: do class and race matter?

The impact of contaminants in water on minorities and economically disadvantaged persons was reviewed. Environmental legislation governing water was summarized as background information against which relevant studies were evaluated. The majority of the available information was anecdotal or case study and did not lend itself to making quantitative comparisons or analyses. However, the data did present certain trends that led to the conclusion that inequities concerning exposure to contaminants in water may exist. The following recommendations were made: current data bases should be analyzed and new data bases created to facilitate assessments of exposure to waterborne contaminants to all populations; an analysis of populations not covered by the Safe Drinking Water Act should be undertaken; a survey should be conducted of the drinking water infrastructure and the results evaluated to identify any impacts to minorities and economically disadvantaged persons; the social, cultural and economic characteristics that influence human exposure to waterborne contaminants need to be identified; and better educational and community outreach programs need to be developed and implemented.

Waterborne disease outbreaks in the United States of America: causes and prevention.

National statistics on waterborne outbreaks in the United States of America show that 1,702 waterborne outbreaks with 542,018 cases of illness and 1,089 deaths have been reported. Almost all deaths prior to 1940 were due to typhoid fever; 9 deaths from other causes have occurred since 1971. During the past decade, 291 waterborne outbreaks were reported in community (43%) and noncommunity (33%) systems, and from the ingestion of contaminated water from recreational (14%) and individual (10%) water sources. Although several large waterborne outbreaks occurred during the past decade, most were in small communities. The number of illnesses per outbreak in noncommunity systems during the past decade is much larger than that reported during any previous period, and the magnitude of these outbreaks indicates the potential effect on the travelling, transient population. During 1981-1990, contaminated, untreated groundwater or inadequately disinfected groundwater was responsible for 43% of all reported waterborne outbreaks, and contaminated, untreated surface water or inadequately treated surface water was responsible for 24% of all reported outbreaks. The use of untreated groundwater has declined in importance as a cause of outbreaks, and more outbreaks are now caused by inadequate or interrupted disinfection of groundwater. The increased occurrence of outbreaks in disinfected groundwater systems may be due to (i) increased use of disinfection with little effort to reduce or eliminate sources of contamination, and (ii) not providing effective, continuous disinfection. In surface-water systems, outbreaks occur primarily because of inadequate or interrupted disinfection in systems that do not provide filtration, but a large increase in outbreaks has recently occurred in filtered systems.(ABSTRACT TRUNCATED AT 250 WORDS)

Waterborne-disease outbreaks, 1989-1990.

For the 2-year period 1989-1990, 16 states reported 26 outbreaks due to water intended for drinking; an estimated total of 4,288 persons became ill in these outbreaks. Giardia lamblia was implicated as the etiologic agent for seven of the 12 outbreaks in which an agent was identified. The outbreaks of giardiasis were all associated with ingestion of unfiltered surface water or surface-influenced groundwater. An outbreak with four deaths was attributed to Escherichia coli O157:H7, the only bacterial pathogen implicated in any of the outbreak investigations. An outbreak of remitting, relapsing diarrhea was associated with cyanobacteria (blue-green algae)-like bodies, whose role in causing diarrheal illness is being studied. Two outbreaks due to hepatitis A and one due to a Norwalk-like agent were associated with use of well water. Eighteen states reported a total of 30 outbreaks due to the use of recreational water, which resulted in illness for an estimated total of 1,062 persons. These 30 reports comprised 13 outbreaks of whirlpool- or hot tub-associated Pseudomonas folliculitis; 13 outbreaks of swimming-associated gastroenteritis, including five outbreaks of shigellosis; one outbreak of hepatitis A associated with a swimming pool; and three cases of primary amebic meningoencephalitis caused by Naegleria. The national surveillance of outbreaks of waterborne diseases, which has proceeded for 2 decades, continues to be a useful means for characterizing the epidemiology of waterborne diseases.

Chlorination, water hardness and serum cholesterol in forty-six Wisconsin communities.

The Wisconsin Heart Health Research Program measured serum lipids and other clinical parameters among residents of 46 neighbouring small communities in central Wisconsin. The purpose of the study was to determine whether distribution of serum lipids, blood pressure or thyroid hormones differed according to the chlorination of water supply, or to its calcium and magnesium content (hardness). This report examines serum lipid levels in relation to the drinking water characteristics chlorination and hardness. Variables measured on individuals included age, education level, alcohol intake, cigarette smoking, dietary fat and dietary calcium. An analysis of covariance was used to estimate effects of chlorination and hardness on each of the serum lipids, with individual variables included as covariates. Among females, serum cholesterol (SC) levels are significantly higher in chlorinated communities than in non-chlorinated communities. Community SC levels are also higher for males in chlorinated communities, on the average, but differences are smaller and not statistically significant. Low density lipoprotein (LDL) cholesterol levels follow a similar pattern to that for total SC levels, higher in chlorinated communities for females, but not different for males. On the other hand, high density lipoprotein (HDL) cholesterol community means are nearly identical in the chlorinated and non-chlorinated communities for each sex.

Waterborne disease outbreaks, 1986-1988.

From 1986 to 1988, 24 states and Puerto Rico reported 50 outbreaks of illness due to water that people intended to drink, affecting 25,846 persons. The protozoal parasite Giardia lamblia was the agent most commonly implicated in outbreaks, as it has been for the last 10 years; many of these outbreaks were associated with ingestion of chlorinated but unfiltered surface water. Shigella sonnei was the most commonly implicated bacterial pathogen; in outbreaks caused by this pathogen, water supplies were found to be contaminated with human waste. Cryptosporidium contamination of a chlorinated, filtered public water supply caused the largest outbreak during this period, affecting an estimated 13,000 persons. A large multistate outbreak caused by commercially produced ice made from contaminated well water caused illness with Norwalk-like virus among an estimated 5,000 persons. The first reported outbreak of chronic diarrhea of unknown cause associated with drinking untreated well water occurred in 1987. Twenty-six outbreaks due to recreational water use were also reported, including outbreaks of Pseudomonas dermatitis associated with the use of hot tubs or whirlpools, and swimming-associated shigellosis, giardiasis, and viral illness. Although the total number of reported water-related outbreaks has been declining in recent years, the few large outbreaks due to Cryptosporidium, Norwalk-like agent, Shigella sonnei, and Giardia lamblia caused more cases of illness in 1987 than have been reported to the Water-Related Disease Outbreak Surveillance System for any other year since CDC and the Environmental Protection Agency began tabulating these data in 1971.

Review of epidemiologic studies of aluminium and neurological disorders.

The epidemiological study of neurological disorders is just beginning and should he continued because of the potential public health impact of these diseases on society. The most important contribution of epidemiological research is the identification of risk factors, and specific disease entities, such as Alzheimer's disease, should be studied.Ecological analysis of geographical data have associated a small increase in mortality from Alzheimer's disease and dementia with the aluminium content of drinking water. These results must necessarily be interpreted with caution because serious errors may result from inferences based on ecological analysis,e.g. "the ecologic fallacy".Potential risk factors for Alzheimer's disease have been studied in case-comparison epidemiology studies conducted in Italy, Massachusetts, Colorado, Minnesota and North Carolina, but only two studies have considered aluminium exposure, through the use of antacids. Although no increased risk was found to be associated with aluminium exposure, only a small number of individuals in the studies reported antacid use, and the studies had an extremely limited statistical power to detect an association.Additional analytical epidemiology studies, either cohort or case-comparison, are required to better describe the possible relationship between aluminium and Alzheimer's disease. These studies should be designed according to well-established epidemiological principles, be conducted with no selection bias and minimum observation bias, consider potential confounding and modifying factors, and have sufficient statistical power to enable detection of low relative risks.