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.     

Outbreak of gastroenteritis associated with an interactive water fountain at a beachside park--Florida, 1999

Since 1989, approximately 170 outbreaks associated with recreational water venues (e.g., swimming pools, waterparks, fountains, hot tubs and spas, lakes, rivers, and oceans) have been reported, with almost half resulting in gastrointestinal illness (1-5). This report summarizes the investigation of an outbreak of gastroenteritis in Florida during 1999. The findings indicated that Shigella sonnei and Cryptosporidium parvum infections caused illness in persons exposed to an "interactive" water fountain at a beachside park.     

A review of outbreaks of waterborne disease associated with ships: evidence for risk management

OBJECTIVE: The organization of water supply to and on ships differs considerably from that of water supply on land. Risks of contamination can arise from source water at the port or during loading, storage, or distribution on the ship. The purpose of this article is to review documented outbreaks of waterborne diseases associated with passenger, cargo, fishing, and naval ships to identify contributing factors so that similar outbreaks can be prevented in the future. METHODS: The authors reviewed 21 reported outbreaks of waterborne diseases associated with ships. For each outbreak, data on pathogens/toxins, type of ship, factors contributing to outbreaks, mortality and morbidity, and remedial action are presented. RESULTS: The findings of this review show that the majority of reported outbreaks were associated with passenger ships and that more than 6,400 people were affected. Waterborne outbreaks due to Enterotoxigenic Escherichia coli, noroviruses, Salmonella spp, Shigella sp, Cryptosporidium sp, and Giardia lamblia occurred on ships. Enterotoxigenic E. coli was the pathogen most frequently associated with outbreaks. One outbreak of chemical water poisoning also occurred on a ship. Risk factors included contaminated port water, inadequate treatment, improper loading techniques, poor design and maintenance of storage tanks, ingress of contamination during repair and maintenance, cross-connections, back siphonage, and insufficient residual disinfectant. CONCLUSIONS: Waterborne disease outbreaks on ships can be prevented. The factors contributing to outbreaks emphasize the need for hygienic handling of water along the supply chain from source to consumption. A comprehensive approach to water safety on ships is essential. This may be achieved by the adoption of Water Safety Plans that cover design, construction, operation, and routine inspection and maintenance.     

An outbreak of waterborne giardiasis associated with heavy water runoff due to warm weather and volcanic ashfall

From mid-June through early August 1980, an outbreak of gastrointestinal illness in Red Lodge, Montana affected approximately 780 persons, as estimated from attack rates of 33 per cent and 15 per cent in urban and rural residents, respectively. Giardia lamblia was identified in stool specimens from 51 per cent of 47 persons with a history of untreated gastrointestinal illness and in 13 per cent of 24 specimens from asymptomatic persons (p = .00045, Fisher's Exact Test). The epidemic curve was bimodal with peaks in mid-June and mid-July. Each peak occurred about three weeks after an episode of very heavy water runoff resulting from warm sunny weather and snow darkened by ashfall from the Mt. St. Helens volcanic eruption of May 18, 1980. Unfiltered and inadequately chlorinated surface water was supplied by the city water system, which was implicated as the vehicle of transmission in the outbreak. Water systems providing unfiltered surface water are more likely to become contaminated during periods of heavy water runoff.     

Prolonged outbreak of giardiasis with two modes of transmission

Large outbreaks of giardiasis caused by person-to-person transmission, or a combination of transmission routes, have not previously been reported. A large, prolonged giardiasis outbreak affected families belonging to a country club in a suburb of Boston, Massachusetts, during June-December 2003. We conducted a retrospective cohort study to determine the source of this outbreak. Giardiasis-compatible illness was experienced by 149 (25%) respondents to a questionnaire, and was laboratory confirmed in 97 (65%) of these cases. Of the 30 primary cases, exposure to the children's pool at the country club was significantly associated with illness (risk ratio 3.3, 95% confidence interval 1.7-6.5). In addition, 105 secondary cases probably resulted from person-to-person spread; 14 cases did not report an onset date. This outbreak illustrates the potential for Giardia to spread through multiple modes of transmission, with a common-source outbreak caused by exposure to a contaminated water source resulting in subsequent prolonged propagation through person-to-person transmission in the community. This capacity for a common-source outbreak to continue propagation through secondary person-to-person spread has been reported with Shigella and Cryptosporidium and may also be a feature of other enteric pathogens having low infectious doses.     

Multi-pathogen waterborne disease outbreak associated with a dinner cruise on Lake Michigan

We report an outbreak associated with a dinner cruise on Lake Michigan. This took place on the same day as heavy rainfall, which resulted in 42·4 billion liters of rainwater and storm runoff containing highly diluted sewage being released into the lake. Of 72 cruise participants, 41 (57%) reported gastroenteritis. Stool specimens were positive for Shigella sonnei (n=3), Giardia (n=3), and Cryptosporidium (n=2). Ice consumption was associated with illness (risk ratio 2·2, P=0·011). S. sonnei was isolated from a swab obtained from the one of the boat's ice bins. Environmental inspection revealed conditions and equipment that could have contributed to lake water contaminating the hose used to load potable water onto the boat. Knowledge of water holding and distribution systems on boats, and of potential risks associated with flooding and the release of diluted sewage into large bodies of water, is crucial for public health guidance regarding recreational cruises.     

An outbreak of shigellosis at an outdoor music festival

In August 1988, an estimated 3,175 women who attended a 5-day outdoor music festival in Michigan became ill with gastroenteritis caused by Shigella sonnei. Onset of illness peaked 2 days after the festival ended, and patients were spread throughout the United States by the time the outbreak was recognized. An uncooked tofu salad served on the last day was implicated as the outbreak vehicle (odds ratio = 3.4, p less than 0.0001). Over 2,000 volunteer food handlers prepared the communal meals served during the festival. This large foodborne outbreak had been heralded by a smaller outbreak of shigellosis among staff shortly before the festival began and by continued transmission of shigellosis from staff to attendees during the festival. S. sonnei isolated from women who became ill before, during, and after the festival had identical antimicrobial susceptibility patterns and plasmid profiles. Limited access to soap and running water for handwashing was one of the few sanitary deficits noted at this gathering. This investigation demonstrates the need for surveillance and prompt public health intervention when Shigella infections are recognized in persons attending mass outdoor gatherings, the singular importance of handwashing in reducing secondary transmission of shigellosis, and the potential for explosive outbreaks when communal meals are prepared by large numbers of food handlers.     

Contaminated produce--a common source for two outbreaks of Shigella gastroenteritis

Simultaneous outbreaks of Shigella sonnei gastroenteritis occurred in October 1983 at two Texas university campuses 60 miles (96 km) apart. There were no common food handlers, recreational activities, water sources or swimming areas to explain the introduction of Shigella at both campuses. However, tossed salads were found to be associated with illness at both campuses. The investigation disclosed that both schools had received produce shipments from the same company during the week preceding these outbreaks. Shigella isolates from cases at both universities, sent to the Centers for Disease Control for plasmid analysis and colicin typing, were found to be identical. The same organism was evidently not a frequent cause of shigellosis within a 160-mile (256 km) radius of these universities since only 19% of control isolates chosen from this area were identical to the type which caused these outbreaks. This is the first report of two related outbreaks of shigellosis that were caused by a contaminated food source and not by a food handler. Simultaneous foodborne outbreaks of shigellosis should trigger a search for potential contamination at every step of food handling from farm to kitchen.     

Case-control study of waterborne giardiasis in Reno, Nevada

An outbreak of Giardia lamblia gastroenteritis occurred in Reno, Nevada, in 1982, during which 324 laboratory-confirmed infections were reported. During the outbreak, Reno was supplied in part by surface water that was chemically coagulated, settled, and chlorinated, but was not filtered. Giardia cysts were recovered from the water supply, and a beaver infected with Giardia was found in one of the reservoirs. A case-control study indicated that, during the outbreak but not afterwards, persons with giardiasis drank more municipal water than did controls. Corrective measures, which included removing the infected beaver and increasing the chlorine concentration, were followed by a rapid decrease in reports of giardiasis.     

Outbreaks associated with recreational water in the United States

In this article, we review the causes of outbreaks associated with recreational water during 1971-2000. A bacterial or protozoan etiology was identified in three-quarters of the outbreaks; 23% of the outbreaks were of undetermined etiology. The most frequently identified agents were Cryptosporidium (15%), Pseudomonas (14%), Shigella (13%), Naegleria (11%), Giardia (6%), and toxigenic E. coli (6%). Outbreaks attributed to Shigella, E. coli O157:H7, and Naegleria were primarily associated with swimming in fresh waters such as lakes, ponds, and rivers. In contrast, outbreaks caused by Cryptosporidium and Giardia were primarily associated with treated water in swimming and wading pools. Important sources of contamination for both treated and untreated recreational waters were the bathers themselves. Contamination from sewage discharges and wild or domestic animals were also important sources for untreated waters. Contributing factors in swimming-pool outbreaks were inadequate attention to maintenance, operation, disinfection, and filtration. Although not all waterborne outbreaks are recognized nor reported, the national surveillance of these outbreaks has helped identify important sources of contamination of recreational waters and the etiologic agents. This information can affect prevention recommendations and research priorities that may lead to improved water quality guidelines.     

Beobachtungen über parasitenbedingte Ausbrüche durch Trinkwasser und Maßnahmen zu deren Vermeidung Teil II: Literaturüberblick über trinkwasserbedingte Ausbrüche durch Giardia lamblia, Cryptosporidium parvum und Toxoplasma gondii

Measures to guarantee a high quality of drinking water are based upon the observations and scientific results of former outbreaks. Two “new” pathogen organisms –Cryptosporidium parvum and Giardia lamblia– which can be transmitted by drinking water, have emerged. Beyond that there was an outbreak in 1994/95 for the first time by Toxoplasma gondii, an organism which is already well known for a long time. Because of the parasitic outbreaks it has to be proved whether the usual measures are sufficient. In the paper 29 outbreaks by Giardia lamblia, 37 by Cryptosporidium parvum and 1 by Toxoplasma gondii are listed with more than 100 cases of illness and the circumstances for the transmission of the organisms with drinking water.     

A shigellosis outbreak traced to commercially distributed shredded lettuce

In the period August 30-October 7, 1986, 347 persons in adjacent west Texas counties (Ector and Midland) contracted culture-confirmed Shigella sonnei gastroenteritis. A case-control study showed an increased risk of acquiring shigellosis in Ector County with eating at outlets of fast-food Restaurant A, and in Midland County with eating at Restaurant B or C. A second case-control study, of persons who had eaten at Ector County outlets of Restaurant A, showed an increased risk of acquiring shigellosis with eating foods containing shredded lettuce and tomatoes, which were served together (odds ratio = 68.8; 95% confidence interval 8.5-293.1). All implicated restaurants received shredded lettuce produced at one lettuce-shredding plant; two implicated restaurants did not receive tomatoes from the lot delivered to other implicated restaurants. The lettuce-shredding plant distributed shredded lettuce and intact lettuce; restaurants that received only intact lettuce were not involved in the outbreak. Investigation at the lettuce-shredding plant suggested that a food handler might have been the source of contamination and that the method of processing might have allowed cross-contamination to occur. In the laboratory, the outbreak strain of S. sonnei multiplied rapidly on shredded lettuce at 22 C and survived on refrigerated shredded lettuce for at least seven days. This outbreak, one of the largest outbreaks of Shigella infections in the United States in the last decade, indicates that a large, geographically widespread shigellosis outbreak can result from contaminated shredded lettuce that is distributed commercially.     

Communitywide cryptosporidiosis outbreak--Utah, 2007

Cryptosporidiosis is a nationally notifiable gastrointestinal illness caused by chlorine-resistant protozoa of the genus Cryptosporidium. Fecal-oral transmission of Cryptosporidium occurs via ingestion of contaminated recreational water, drinking water, or food, or via contact with infected persons or animals (e.g., cattle). Incidence peaks in late summer and coincides with the summer swimming season. The number of nonoutbreak cryptosporidiosis cases reported nationally increased from 3,411 cases in 2004 to nearly 8,300 in 2007 (CDC, unpublished data, 2008). This substantial increase (143%) mirrors the increase in the number of nationally reported cryptosporidiosis outbreaks associated with treated recreational water venues (e.g., pools, water parks, and interactive fountains): seven reported treated recreational water-associated outbreaks in 2004, 19 in 2006, and, as of September 5, 2008, provisional reports of 26 in 2007 (CDC, unpublished data, 2008). This report describes a communitywide cryptosporidiosis outbreak in Utah that likely was associated initially with treated recreational water venues and subsequently with person-to-person transmission. Cryptosporidium's ability to cause communitywide outbreaks, which is attributable to factors such as its chlorine resistance, underscores the need for more rapid implementation of control measures once an increase in case reporting is noted rather than waiting for an outbreak investigation to implicate a specific source of transmission. Such a response should include 1) pre-outbreak planning and preparation, 2) pre-outbreak adoption of a disease action threshold (e.g., a twofold to threefold increase in cases over baseline), and 3) rapid mobilization of community partners to implement control measures once the threshold is exceeded.     

A community waterborne gastroenteritis outbreak: evidence for rotavirus as the agent.

A community waterborne nonbacterial gastroenteritis outbreak occurred in Eagle-Vail, Colorado in March 1981. Illness (defined as vomiting and/or diarrhea) was statistically associated with water consumption (chi 2 for linear trend = 7.07, p less than .005). Five of seven persons associated with the outbreak were infected with rotavirus as shown by virus detection or serological methods. Bacterial pathogens, Giardia lamblia, and Norwalk virus were excluded as responsible agents. Rotavirus should be looked for as a cause of waterborne outbreaks.     

General outbreaks of infectious intestinal disease linked with salad vegetables and fruit,England and Wales, 1992-2000

Between 1992 and 2000, 1,518 foodborne general outbreaks of infectious intestinal disease (IID) were reported to the Public Health Laboratory Service (PHLS) Communicable Disease Surveillance Centre (CDSC), of which 83 (5.5%) were associated with the consumption of salad vegetables or fruit (SVF). The pathogens most frequently reported were salmonellas (41.0%) and Norwalk-like virus (NLV) (15.7%). In total 3,438 people were affected; 69 were admitted to hospital and one person died. Most outbreaks were linked to commercial catering premises (67.5%). Three community outbreaks, of Salmonella enterica serovar Typhimurium Definitive Phage Type (DT) 104, S. Typhimurium DT 204b and Shigella sonnei infection, were found to be associated with lettuce contaminated at source, and these accounted for 501 (14.6%) cases. The latter two outbreaks were international, involving several European countries. This demonstrates how contamination of SVF during production/processing can result in major, geographically widespread, outbreaks of infection with serious public health consequences.     

A review of outbreaks of foodborne disease associated with passenger ships: evidence for risk management

OBJECTIVE: Foodborne disease outbreaks on ships are of concern because of their potentially serious health consequences for passengers and crew and high costs to the industry. The authors conducted a review of outbreaks of foodborne diseases associated with passenger ships in the framework of a World Health Organization project on setting guidelines for ship sanitation. METHODS: The authors reviewed data on 50 outbreaks of foodborne disease associated with passenger ships. For each outbreak, data on pathogens/toxins, type of ship, factors contributing to outbreaks, mortality and morbidity, and food vehicles were collected. RESULTS: The findings of this review show that the majority of reported outbreaks were associated with cruise ships and that almost 10,000 people were affected. Salmonella spp were most frequently associated with outbreaks. Foodborne outbreaks due to enterotoxigenic E. coli spp, Shigella spp, noroviruses (formally called Norwalk-like viruses), Vibrio spp, Staphylococcus aureus, Clostridium perfringens, Cyclospora sp, and Trichinella sp also occurred on ships. Factors associated with the outbreaks reviewed include inadequate temperature control, infected food handlers, contaminated raw ingredients, cross-contamination, inadequate heat treatment, and onshore excursions. Seafood was the most common food vehicle implicated in outbreaks. CONCLUSIONS: Many ship-associated outbreaks could have been prevented if measures had been taken to ensure adequate temperature control, avoidance of cross-contamination, reliable food sources, adequate heat treatment, and exclusion of infected food handlers from work.     

Cryptosporidiosis outbreaks associated with recreational water use--five states, 2006

Cryptosporidiosis is a gastrointestinal illness caused by parasitic protozoa of the genus Cryptosporidium and can produce watery diarrhea lasting 1-3 weeks; one or two cases per 100,000 population are reported annually in the United States. Fecal-oral transmission of Cryptosporidium oocysts occurs through ingestion of contaminated drinking or recreational water, consumption of contaminated food, and contact with infected persons or animals (e.g., cattle or sheep). Unlike bacterial pathogens, Cryptosporidium oocysts are resistant to chlorine disinfection and can survive for days in treated recreational water venues (e.g., public and residential swimming pools and community and commercial water parks) despite adherence to recommended residual chlorine levels (1-3 ppm). For 2006, a total of 18 cryptosporidiosis outbreaks have been reported (as of July 24, 2007) to CDC's U.S. Waterborne Disease and Outbreak Surveillance System, compared with five outbreaks reported for 2003 and seven for 2004; data for 2005 and 2006 are not yet final. This report describes five laboratory-confirmed cryptosporidiosis outbreaks in 2006 that involved public recreational water use. The popularity of recreational water venues, the number and geographic distribution of recent cryptosporidiosis outbreaks, and the resistance of Cryptosporidium to chlorination suggest that treatment strategies for recreational water facilities need to be improved.     

Outbreak of Norwalk virus in a Caribbean island resort: application of molecular diagnostics to ascertain the vehicle of infection

In 1998, an outbreak of gastroenteritis affected at least 448 persons including 122 staff at a resort hotel in Bermuda. A survey among staff indicated that gastroenteritis was associated with eating or drinking at the hotel (OR = 60, 95% CI = 2.4-15.1). Multiple specimens of drinking water had elevated faecal coliform levels and Escherichia coli present, suggestive of faecal contamination. Stools from 18 of the 19 persons with gastroenteritis that were tested were positive for genogroup-II Norwalk-like viruses (NLVs). RT-PCR analysis of a 31 specimen of water produced a genogroup-II NLV genome with a sequence identical to that of NLVs in the stools of three ill persons. This outbreak shows the value of new molecular diagnostics to link illness with a contaminated source through the use of sequence analysis. The risk of outbreaks such as these could be reduced in tourism dependent regions like Bermuda and the Caribbean by regular evaluation of data from the inspection and monitoring of drinking water supplies and waste water systems, by ensuring the chlorination of supplemental drinking water supplies and by establishing food-safety initiatives.     

Durch Trinkwasser übertragene parasitäre Zoonosen

Nowadays, the parasitic zoonose organisms Giardia lamblia und Cryptosporidium spp. are among the most relevant pathogens of drinking water-associated disease outbreaks. These pathogens are transmitted via a fecal-oral route; in both cases the dose of infection is low. Apart from person-to-person or animal-to-person transmissions, the consumption of contaminated food and water are further modes of transmission. The disease is mainly characterized by gastrointestinal symptoms. In industrialized countries, the prevalence rate of giardiasis is 2-5 % and of cryptosporidiosis 1-3%. Throughout the world, a large number of giardiasis and cryptosporidiosis outbreaks associated with drinking water were published; in 2001 the first case in Germany was identified. Giardia and Cryptosporidium are detected in surface water and sporadically in unprotected groundwater. Use of these waters for drinking water abstraction makes high demands on the technology of the treatment process: because of the disinfectant resistance of the parasites, safe elimination methods are needed, which even at high contamination levels of source water guarantee safe drinking water. Further measures for prevention and control are implementation of the HACCP concept, which includes the whole chain of procedures of drinking water supply from catchment via treatment to tap and a quality management system.     

Infectious disease outbreaks related to drinking water in Canada, 1974-2001

BACKGROUND: Recent public attention on drinking water supplies in the aftermath of waterborne infection outbreaks in Walkerton and North Battleford raises questions about safety. We analyzed information on waterborne outbreaks occurring between 1974 and 2001 in order to identify apparent trends, review the current status of monitoring and reporting, and gain a better understanding of the impact of drinking water quality on public health and disease burden. METHODS: Data from outbreak investigations, published and unpublished, were categorized by the type of drinking water provider and were assessed to be definitely, probably or possibly waterborne in nature. RESULTS: The final data set consisted of 288 outbreaks of disease linked to a drinking water source. There were 99 outbreaks in public water systems, 138 outbreaks in semi-public systems and 51 outbreaks in private systems. The main known causative agents of waterborne disease outbreaks were (in descending frequency of occurrence) Giardia, Campylobacter, Cryptosporidium, Norwalk-like viruses, Salmonella and hepatitis A virus. SUMMARY: We found that severe weather, close proximity to animal populations, treatment system malfunctions, poor maintenance and treatment practices were associated with the reported disease outbreaks resulting from drinking water supplies. However, issues related to the accuracy, co-ordination, compatibility and detail of data exist. A systematic and coordinated national surveillance system for comparison purposes, trend identification and policy development is needed so that future waterborne disease outbreaks can be avoided.