Cryptosporidiosis in children during a massive waterborne outbreak in Milwaukee,Wisconsin: clinical,laboratory and epidemiologic findings.

During the spring of 1993 an estimated 403000 residents of the greater Milwaukee, Wisconsin area experienced gastrointestinal illness due to infection with the parasite Cryptosporidium parvum following contamination of the city''s water supply. To define the clinical, laboratory and epidemiologic features of outbreak-associated cryptosporidiosis in children, medical and laboratory records for all children submitting stool samples to the microbiology laboratory of the Children''s Hospital of Wisconsin between 7 April and 13 May 1993 were reviewed retrospectively. Interviews with parents were also conducted to obtain additional clinical history. Cryptosporidium, as the sole pathogen, was identified in stools from 49 (23%) of the 209 children enrolled in the study. Children with laboratory-confirmed cryptosporidiosis were more likely to live in areas of Milwaukee supplied with contaminated water (RR = 1.92, CI = 1.19-3.09), to be tested later in their illness (P < 0.05), to have submitted more than one stool specimen (P = 0.01), to have an underlying disease that altered their immune status (RR = 2.78, CI = 1.60-4.84), and to be older than 1 year of age (RR = 2.02, CI = 1.13-3.60). Clinical illness in these patients was more prolonged and associated with weight loss and abdominal cramps compared with Cryptosporidium-negative children. In the context of this massive waterborne outbreak relatively few children had documented infection with Cryptosporidium. If many children who tested negative for the parasite were truly infected, as the epidemiologic data suggest, existing laboratory tests for Cryptosporidium were insensitive, particularly early in the course of illness.     

Cost of illness in the 1993 waterborne Cryptosporidium outbreak,Milwaukee, Wisconsin

To assess the total medical costs and productivity losses associated with the 1993 waterborne outbreak of cryptosporidiosis in Milwaukee, Wisconsin, including the average cost per person with mild, moderate, and severe illness, we conducted a retrospective cost-of-illness analysis using data from 11 hospitals in the greater Milwaukee area and epidemiologic data collected during the outbreak. The total cost of outbreak-associated illness was 96.2 million US dollars: 31.7 million US dollars in medical costs and 64.6 million US dollars in productivity losses. The average total costs for persons with mild, moderate, and severe illness were 116 US dollars, 47 US dollars, and 7,808 US dollars, respectively. The potentially high cost of waterborne disease outbreaks should be considered in economic decisions regarding the safety of public drinking water supplies.     

Surveillance data for waterborne illness detection: an assessment following a massive waterborne outbreak of Cryptosporidium infection.

Following the 1993 Milwaukee cryptosporidiosis outbreak, we examined data from eight sources available during the time of the outbreak. Although there was a remarkable temporal correspondence of surveillance peaks, the most timely data involved use of systems in which personnel with existing close ties to public health programmes perceived the importance of providing information despite workload constraints associated with an outbreak. During the investigation, surveillance systems which could be easily linked with laboratory data, were flexible in adding new variables, and which demonstrated low baseline variability were most useful. Geographically fixed nursing home residents served as an ideal population with nonconfounded exposures. Use of surrogate measurements of morbidity can trigger worthwhile public health responses in advance of laboratory-confirmed diagnosis and help reduce total morbidity associated with an outbreak. This report describes the relative strengths and weaknesses of these surveillance methods for community-wide waterborne illness detection and their application in outbreak decision making.     

The elderly and waterborne Cryptosporidium infection: gastroenteritis hospitalizations before and during the 1993 Milwaukee outbreak

We used the Temporal Exposure Response Surfaces modeling technique to examine the association between gastroenteritis-related emergency room visits and hospitalizations in the elderly and drinking water turbidity before and during the 1993 Milwaukee waterborne Cryptosporidium outbreak. Before the outbreak, the rate of such events increased with age in the elderly (p相似文献   

The role of disease transmission and conferred immunity in outbreaks: analysis of the 1993 Cryptosporidium outbreak in Milwaukee, Wisconsin

The authors examined two competing hypotheses regarding the cause of the 1993 Cryptosporidium outbreak in Milwaukee, Wisconsin. The first was that oocyst contamination of the drinking-water influent, coupled with a treatment plant failure, resulted in a point-source outbreak. The second was that the outbreak was the result of transmission processes that amplified the oocyst concentration in the drinking-water effluent. Analysis of the model suggested that 1) transmission directly from person to person contributed 10% (95% confidence interval: 6%, 21%) of the total cases; 2) closing the drinking-water plant prevented 19% (95% confidence interval: 17%, 21%) of the additional cases of disease that occurred compared with the scenario in which the plant had not been closed, a result primarily driven by conferred immunity that resulted in depletion of the susceptible population; and 3) the outbreak was caused by a transmission cycle due to infectious persons shedding pathogens into the sewage, environmental transport of these pathogens via Lake Michigan to the drinking-water plant, and infection of susceptible persons via exposure to drinking water. The incidence data were consistent with this hypothesis. Further simulations suggested that increasing the distance between the wastewater effluent and the drinking-water influent may have prevented the outbreak.     

Occupational risks during a monkeypox outbreak, Wisconsin, 2003

We determined factors associated with occupational transmission in Wisconsin during the 2003 outbreak of prairie dog--associated monkeypox virus infections. Our investigation included active contact surveillance, exposure-related interviews, and a veterinary facility cohort study. We identified 19 confirmed, 5 probable, and 3 suspected cases. Rash, headache, sweats, and fever were reported by > 80% of patients. Occupationally transmitted infections occurred in 12 veterinary staff, 2 pet store employees, and 2 animal distributors. The following were associated with illness: working directly with animal care (p = 0.002), being involved in prairie dog examination, caring for an animal within 6 feet of an ill prairie dog (p = 0.03), feeding an ill prairie dog (p = 0.002), and using an antihistamine (p = 0.04). Having never handled an ill prairie dog (p = 0.004) was protective. Veterinary staff used personal protective equipment sporadically. Our findings underscore the importance of standard veterinary infection-control guidelines.     

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.     

A waterborne outbreak of hepatitis A in Meade County, Kentucky.

In November 1982, Meade County, Kentucky health officials noted a sudden increase in the incidence of hepatitis A. Using a standardized interview of 73 cases (68 serologically confirmed), and 85 controls (all negative for antibody to hepatitis A virus), the most important risk factor identified was household use of untreated water from a single spring. A dose-response relationship was found for consumption of unboiled spring water. Water samples taken from the spring during the outbreak were contaminated with fecal coliforms.     

A two-year follow-up survey of antibody to Cryptosporidium in Jackson County,Oregon following an outbreak of waterborne disease.

To estimate the duration of Cryptosporidium-specific antibody, a Western blot assay measured antibody in paired sera from 124 residents of Jackson County, Oregon collected 0.5 and 2.5 years after the end of an outbreak in Talent, Jackson County. The outcome measure was the intensity of antibody responses, (which may approximate to a titre), to 27-kDa and 15/17-kDa antigens. Intensity of response to the 27-kDa antigen(s) declined to 54% of the 1992 value while responses to a 15/17-kDa antigen(s) remained close to the initial values. Increasing age of the donor predicted higher intensity of antibody to the 15/17-kDa antigen(s) in both the initial (P = 0.004) and follow-up (P = 0.038) surveys. No relationship was observed between age and antibody intensity for the 27-kDa antigen(s) during either survey (P > 0.10). Both the initial and follow-up surveys showed significant elevations in antibody intensity for Talent residents, possibly indicating a high endemic rate of infection/re-infection or high levels of chronic infection.     

Gastroenteritis: a waterborne outbreak affecting 1600 people in a small Danish town.

STUDY OBJECTIVE--To examine (i) the extent of illness caused by contamination of a waterworks with waste water due to overflow, and its correlation with precipitation; (ii) the potential secondary spread; (iii) economic losses due to sick leave. DESIGN--A historical follow up study with structured postal questionnaires. SETTING--A small community on the outskirts of greater Copenhagen at the end of 1991 and the beginning of 1992. PARTICIPANTS--The main study group comprised all 703 households supplied by the waterworks (response rate: 89% of households). There was a control group of 200 randomly chosen households in neighbouring communities with a different water supply source (response rate: 64% of households). A day care group of all 149 children (response rate: 78%) and 30 teachers (response rate: 83%) who lived in central Copenhagen, but spent the day in four day care centres supplied by the waterworks, and members of their household was also studied. MEASUREMENTS AND MAIN RESULTS--Altogether 1455 people (88% of respondents in the main study group) reported having had symptoms of gastroenteritis, particularly diarrhoea (83%) and vomiting (55%). In the control group, 10% had had symptoms of gastroenteritis. The onset of episodes with diarrhoea correlated well with precipitation (Spearman's correlation coefficient: 0.75; p = 0.0002). The secondary attack rate in household contacts was 12%. No pathogens were found. Affected people stayed home from work for a total of 1658 days. The cost of loss of production because of sick leave amounted to 1,600,000 Danish kroner (180,000 pounds). CONCLUSIONS--The outbreak caused extensive illness correlated with precipitation, showed secondary spread, and was associated with major economic losses. Increased awareness among local physicians and waterworks personnel of the possibility of contamination of the water could have led to earlier intervention and reduced the extent of illness. Outbreaks are often caused by several factors, many of a technical nature, which in this case acted together. It is recommended that attention be paid to each factor.     

An outbreak of waterborne cryptosporidiosis in Swindon and Oxfordshire.

An outbreak of cryptosporidiosis resulted in 516 cases in Wiltshire and Oxfordshire. The outbreak caused widespread interest and led to an official inquiry. The majority of cases were in children; 8% of cases were admitted to hospital and the median duration of illness was 3 weeks. The geographical distribution of cases matched the distribution of water supplies from three treatment works and cryptosporidium oocysts were found at these works and in the treated water. Attack rates in electoral wards supplied by the three treatment works were significantly higher than in other wards. The cause of the outbreak appeared to be the failure of normal treatment to remove oocysts. Measures at the treatment works reduced the number of oocysts detected in treated water, after which the outbreak came to an end. The conclusion of the investigations was that cryptosporidiosis is a risk of conventionally treated public water supplies.     

Leptospirosis on Kauai: investigation of a common source waterborne outbreak.

During the summer of 1987, a common source waterborne outbreak of leptospirosis occurred on the island of Kauai in the state of Hawaii. Eight leptospirosis cases were identified using the microscopic agglutination test. Methodologic weaknesses in this technique were responsible for the initial missed diagnosis on six of the eight cases. All cases had repeated exposure to the Waimea River. A wide array of animal reservoirs and optimal water conditions may have been factors in this outbreak.     

Kawasaki syndrome: a controlled study of an outbreak in Wisconsin

The etiology of Kawasaki syndrome remains unestablished, although a possible role has been suggested for exposure to the application of carpet shampoo, house dust mites, and rickettsial infection. During an outbreak of 20 cases of Kawasaki syndrome that occurred in southeastern Wisconsin from November 1982 through March 1983, a case-control study was done of 15 cases and 30 matched controls. The study included questionnaire administration, dust collection from homes, and serum specimen collection. Only one patient had been exposed to a shampooed carpet within 30 days before onset of illness. No differences were noted between cases and controls in the degree of exposure to house dust mite-associated factors in the home, nor in the occurrence, density and species-specific prevalence of house dust mites in the home. Meadow voles exposed to house dust mites from the homes of patients did not develop serologic or pathologic evidence of infection due to rickettsiae in the spotted fever and typhus groups or Coxiella burnetii. Anti-mite-specific immunoglobulin E was not detected in serum specimens from cases or controls. Results from this study do not support hypotheses suggesting that the development of Kawasaki syndrome is associated with exposure to application of carpet shampoo, house dust mites, or rickettsial infection.