Shigellosis outbreak associated with swimming

In June 1982, an outbreak of gastrointestinal illness caused by Shigella sonnei occurred among residents of two counties in Oklahoma. A case-control study of cases and age and sex-matched controls showed an association with attendance at a southern Oklahoma lake (14/17 cases vs 3/17 controls, matched pair odds ratio [OR] 9/0, confidence interval [CI] 2.4-infinity). A survey of 85 persons who had visited the lake area showed that persons who had swum were more likely to have been ill with a gastrointestinal illness (50 per cent) than persons who had not swum (0 per cent); among those who had swum, illness was more frequent among those who reported having water in their mouths while swimming (62 per cent) than those who did not (19 per cent) (OR = 6.9, 95% CI = 2.2-21.5). No further primary lake-associated cases had onset of symptoms beyond two days of closing the reservoir. Swimming should be considered as a potential source of enteric infections.     

Epidemic campylobacteriosis associated with a community water supply.

In May 1983, an estimated 865 cases of epidemic gastrointestinal disease occurred in Greenville, Florida. Surveillance of pharmacy sales of antidiarrheal medicines suggested that the outbreak was confined to Greenville and its immediate vicinity. Surveys demonstrated that the gastrointestinal illness attack rates inside and outside the city limits were 56 per cent (72/128) and 9 per cent (7/77), respectively (relative risk (RR) = 6.2); consumption of city water was associated with illness (RR = 12); and as water consumption increased, the attack rate also increased (p less than 0.001). Four adults were hospitalized and one outbreak-related case of Guillain-Barre' syndrome was identified. Campylobacter jejuni was isolated from specimens from 11 ill persons; serologic studies showed the development of Campylobacter-specific antibodies. Fecal coliforms were found in water samples, but Campylobacter was not recovered from water. The city water plant, a deep well system, had numerous deficiencies including an unlicensed operator, a failure of chlorination, and open-top treatment towers. Birds were observed perching on the open-top treatment tower. Of 38 birds trapped seven weeks later, 37 per cent harbored C. jejuni; however, plasmid and serotyping studies showed that strains were not the same as the common strain from ill persons. This outbreak suggests that water systems that are unprotected from contact with birds may become contaminated and a source of outbreaks of human campylobacteriosis.     

An outbreak of gastrointestinal illness associated with the consumption of escolar fish.

An outbreak of gastrointestinal illness occurred amongst attendees of a conference lunch in the Hunter area, New South Wales, in October 2001. A distinctive symptom reported by many ill persons was the presence of oily diarrhoea. The Hunter Public Health Unit investigated the outbreak by conducting a telephone interview of the cohort of conference attendees using a standard questionnaire. Twenty persons out of 44 attendees (46%) became ill following the conference. The median incubation period was 2.5 hours (range 1-90 hours). The most common symptoms reported were; diarrhoea (80%)-38 per cent of these reported oily diarrhoea; abdominal cramps (50%); nausea (45%); headache (35%) and vomiting (25%). For analyses, a case was defined as a person who developed oily diarrhea, or diarrhoea within 48 hours, or had at least two other symptoms of gastroenteritis within 6 hours, of the conference lunch. Seventeen persons had symptoms that met the case definition. None of the foods or beverages consumed were significantly associated with illness, however, all cases had consumed fish and none of those who did not eat fish (4 persons) became ill. Moreover, only 'fish' or 'potato chips' could explain a significant proportion of the illness. Analysis of the oil composition of the fish consumed was consistent with the known profile of the species marketed as 'escolar'. Among those who consumed fish the following potential risk factors did not have a significant association with the illness; Body Mass Index, age, health status and the amount of fish consumed. We concluded that consumption of fish within the marketing group escolar can cause severe abdominal cramping, nausea and vomiting, in addition to incontinent diarrhoea.     

Norwalk-related viral gastroenteritis due to contaminated drinking water

An explosive outbreak of gastrointestinal illness clinically compatible with infection by an agent serologically related to Norwalk virus agent occurred in an elementary school in May 1978. Seroconversion by radioimmunoassay to the Norwalk antigen was noted in two of three ill persons, but no viral particles were identified in stool. Illness developed in 72% of students and teachers at the school, and 32% of household contacts of these ill persons. Of household contacts of persons exposed at school but not clinically ill, 11% developed illness. This value, however, was not statistically different from the level of illness observed concurrently in household contacts of students at an unaffected school nearby. Epidemiologic investigation implicated water as the mode of transmission. Average consumption of one or more glasses per day was strongly associated with illness (p less than 0.00000001). Among soccer team members with limited school contact, water consumption at the school was associated with a 14-fold greater risk of illness (p less than 0.000001). Drinking water was most likely contaminated by back-siphonage through a cross-connection between the school's well and septic tank. This contamination occurred approximately 24 to 36 hours before the outbreak developed.     

An outbreak of cryptosporidiosis associated with an animal nursery at a regional fair.

Cryptosporidiosis is a common gastrointestinal illness that is transmitted from infected persons, animals, or contaminated water or food. This article reports on an outbreak of cryptosporidiosis associated with an animal nursery at an agricultural show held in northern Tasmania during October 2001. Eighty-one per cent of cases (38/47) notified to the Tasmanian Department of Health and Human Services over a 35 day period were interviewed to determine potential sources of infection. Eighty-one per cent of interviewed cases (29/36) reported that they had attended the agricultural show, and 75 per cent (27/36) reported contact with animals in the animal nursery. Cases occurring more than one incubation period after the agricultural show were significantly more likely to have had contact with someone else with diarrhoea (p<0.01). This is the first reported outbreak of cryptosporidiosis associated with an animal nursery in Australia. The outbreak demonstrates the importance of infection control policies and hygiene measures in the animal nursery setting.     

Waterborne Gastroenteritis due to the Norwalk Agent: Clinical and Epidemiologic Investigation

An outbreak of gastroenteritis occurred at a Pennsylvania summer camp in July 1978. Symptoms included abdominal pain (81 per cent), nausea (72 per cent), and vomiting (53 per cent); upper respiratory infection symptoms occurred in 35 per cent of the campers. Illness was associated with consumption of five or more glasses of water or water-containing beverages. Stool cultures from affected persons were negative for bacterial pathogens; however, a fourfold or greater rise to the Norwalk agent was demonstrated in serum samples of three of three ill persons tested and in none of eight controls (p < .02). Campers ill during the first session who were also present during the second session did not become ill during the second session (p < .001). (Am J Public Health 1982; 72:72-74.)     

Smoking and epidemic influenza-like illness in female military recruits: a brief survey.

An outbreak of influenza-like disease caused illness among 48 per cent of 173 female military recruits, 35 per cent of whom smoked cigarettes. The risk of influenza-like illness was greater in smokers (60.0 per cent) than in nonsmokers (41.6 per cent), with a risk ratio of 1.44 (95 per cent CL 1.03-2.01). Among those ill, a significantly greater proportion of smokers visited the clinic than nonsmokers. This could have been due to more severe illness among smokers, or to a greater tendency to visit the physician. The proportion of influenza-like disease attributable to smoking in this population was 13 per cent.     

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.     

The risk of acquiring hepatitis from sewage-contaminated water

There is little information on the risk of acquiring hepatitis A from drinking sewage-contaminated water. In a large outbreak of gastrointestinal illness at Crater Lake National Park, Oregon, a US national park, in June-July, 1975, approximately 100,000 persons were exposed to sewage-contaminated water. State health departments reported three cases of Crater Lake-associated hepatitis A for a rate of 12/100,000 per year, comparable to the reported US incidence of non-B hepatitis 10/100,000 per year. Questionnaire survey of 3997 overnight park visitors revealed five cases of hepatitis A, occurring in 2206 persons who drank water but did not receive immune serum globulin (ISG) within two weeks of exposure, an attack rate of 0.23%. The association between drinking park water and subsequently developing hepatitis was not statistically significant. No cases of hepatitis occurred in 320 park staff and family members, repeatedly exposed to contaminated water. The authors do not recommend routine use of prophylactic ISG for similar outbreaks of gastroenteritis caused by sewage-contaminated water but suggest close surveillance of the exposed group, and careful consideration of risk factors and costs.     

Clostridium perfringens food-borne outbreak: an epidemiological investigation

Abstract: On 3 April 1994, the Western Sector Public Health Unit was notified of an outbreak of gastroenteritis at a Christian youth camp. Attending the camp were 820 people; 241 (42 per cent) of 574 camp participants who completed a questionnaire reported illness. Of these, 230 met the case definition. Main symptoms reported were stomach cramps (78 per cent), diarrhoea (67 per cent) and nausea (46 per cent). Bacterial analysis of leftover chicken grew 2.3times10⁷ and 3.3times10⁷ colonies/g of Clostridium perfringens, and we identified Type A enterotoxin of C. perfringens in four of seven stool samples collected from ill people. Camp participants who consumed chicken at lunch on the second day of the camp were nearly four times as likely to be ill than those who did not (relative risk 3.81, 95 per cent confidence interval 3.07 to 4.72). There were deficiencies in hygiene and food preparation. We highlight the importance of time and temperature controls in food preparation and storage to prevent contamination and subsequent poisoning by C. perfringens or other food pathogens. This investigation demonstrates the importance of a multidisciplinary team when investigating disease outbreaks.     

Outbreak of cryptosporidiosis at a California waterpark: employee and patron roles and the long road towards prevention

In August-September 2004, a cryptosporidiosis outbreak affected >250 persons who visited a California waterpark. Employees and patrons of the waterpark were affected, and three employees and 16 patrons admitted to going into recreational water while ill with diarrhoea. The median illness onset date for waterpark employees was 8 days earlier than that for patrons. A case-control study determined that getting water in one's mouth on the waterpark's waterslides was associated with illness (adjusted odds ratio 7.4, 95% confidence interval 1.7-32.2). Laboratory studies identified Cryptosporidium oocysts in sand and backwash from the waterslides' filter, and environmental investigations uncovered inadequate water-quality record keeping and a design flaw in one of the filtration systems. Occurring more than a decade after the first reported outbreaks of cryptosporidiosis in swimming pools, this outbreak demonstrates that messages about healthy swimming practices have not been adopted by pool operators and the public.     

Epidemiologic investigation of a Yersinia camp outbreak linked to a food handler

In July 1981, an outbreak of gastroenteritis occurred at a summer diet camp. Of the 455 campers and staff, 35 per cent developed an illness characterized by abdominal pain, fever, diarrhea, and/or nausea and vomiting. A total of 53 per cent experienced abdominal pain. Seven persons were hospitalized, five of whom had appendectomies. Yersinia enterocolitica serogroup 0:8 was isolated from 37 (54 per cent) of 69 persons examined, including the camp cook and three assistants. An epidemiologic investigation demonstrated that illness was associated with consumption of reconstituted powdered milk and/or chow mein . Y. enterocolitica serogroup 0:8 was subsequently isolated from milk, the milk dispenser, and leftover chow mein . Information obtained during the investigation suggested that the Yersinia had been introduced by a food handler during food-processing procedures.     

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.     

Cryptosporidiosis in Wisconsin: a case-control study of post-outbreak transmission.

During March-April 1993, an estimated 403000 residents of the 5-county greater Milwaukee, Wisconsin area developed cryptosporidiosis after drinking contaminated municipal water. Although the number of cases dropped precipitously after the implicated water plant closed on 9 April, cases continued to occur. To investigate risk factors for post-outbreak cryptosporidiosis, 33 Milwaukee-area residents who had laboratory-confirmed Cryptosporidium infection with onset of diarrhoea between 1 May and 27 June 1993 were interviewed by telephone. Of these, 28 (85%) had onset of diarrhoea during May, 12 (36%) had watery diarrhoea during the outbreak, and 5(15%) were HIV-infected. In a neighbourhood-matched case-control study, immunosuppression (matched odds ratio (MOR) not calculable, 95% confidence interval (CI) 3.0, infinity) and having a child less than 5 years old in the household (MOR = 17.0, CI 2.0, 395.0) were independently associated with infection. When persons who had diarrhoea during the outbreak were excluded, immunosuppression remained significantly associated with illness (MOR not calculable, CI 1.6, infinity). Cryptosporidium transmission continued after this massive waterborne outbreak but decreased rapidly within 2 months.     

Waterborne giardiasis at a mountain resort: evidence for acquired immunity

In November 1981, an outbreak of waterborne giardiasis occurred at a popular ski resort in Colorado. Stratification of illness by consumption of municipal tap water showed a striking dose-response, with an attack rate of 42 per cent among persons who drank six or more glasses of water per day. Filtered water samples revealed Giardia cysts in specimens both before and after treatment, and several deficiencies were found in the water treatment facility. Residents who had lived in the area greater than 2 years had a lower attack rate for illness than short-term residents.     

Foodborne streptococcal pharyngitis Kansas City, Missouri

A foodborne outbreak of streptococcal pharyngitis occurred in association with a meeting of regional blood banking personnel held at a hotel in Kansas City, Missouri, on May 31-June 1, 1984. The incriminated meal was a salad buffet luncheon served on May 31. Of 106 persons identified as eating the luncheon, 60 (56.6 per cent) became ill. The most probable source of infection was an assortment of mousse desserts (p = 0.0532).     

Viral agents of gastroenteritis. Public health importance and outbreak management

Each year, infectious gastroenteritis causes greater than 210,000 children in the United States to be hospitalized and 4-10 million children to die worldwide. Since the mid-1970s, knowledge has increased dramatically concerning the viral agents that are responsible for much of this public health burden. Rotavirus, the most common cause of diarrhea among children, infects virtually every child in the United States by the age of 4 years and causes potentially lethal dehydration in 0.75% of children less than 2 years of age. Other recently identified pathogens include the enteric adenoviruses, calicivirus, astrovirus, and the Norwalk family of agents. Conclusive diagnosis of these viruses requires electron microscopic examination of stool specimens, a laboratory technique that is available only at a few large centers, including CDC. Stool samples from an outbreak that are submitted to CDC for detection of viral pathology should be collected in bulk from 10 ill persons during their first 48 hours of illness, while feces are still liquid, and should be stored at 4 C (not frozen). Acute- and convalescent-phase serum samples should be collected from the same persons, plus from an equal number of controls, during the first week of illness and 3 weeks thereafter. Control measures for outbreaks of viral gastroenteritis should focus on the removal of an ongoing common source of infection (e.g., an ill food handler or the contamination of a water supply) and on the interruption of person-to-person transmission that can perpetuate an outbreak in a population after the common source has been removed. Because improvements in environmental hygiene may not be accompanied by reductions of endemic diarrhea caused by viruses, immunization may play an important role in future control; vaccine trials for rotavirus are in progress. In anticipation of vaccine development and use, CDC recently began national surveillance for the viral agents of gastroenteritis. Health-care facilities involved in the detection of rotavirus or the other viral agents of diarrhea can participate.     

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.     

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.     

A large outbreak of campylobacteriosis associated with a municipal water supply in Finland

In August 1998, an outbreak of campylobacteriosis occurred in one municipality in northern Finland. A 10% random sample of residents (population 15 000) was selected through the National Population Registry for a survey conducted by using postal questionnaires. Cases were defined as residents of the municipality with onset of acute gastroenteritis from 1 to 20 August 1998. Of 1167 respondents (response rate 78%), 218 (18.7%) met the case definition. Drinking non-chlorinated municipal tap water was strongly associated with illness (OR 34.4). The estimated total number of ill persons was 2700. Campylobacter jejuni was isolated from stool samples of 45 (61%) out of 74 patients tested. All five isolates tested had indistinguishable PFGE patterns. Water samples were negative for campylobacter and coliforms. Epidemiological and environmental evidence suggested mains repair as the source of contamination. Non-chlorinated ground-water systems may be susceptible to contamination and can cause large outbreaks.