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      A massive outbreak in Milwaukee of cryptosporidium infection transmitted through the public water supply.

      The New England journal of medicine
      Adolescent, Adult, Aged, Animals, Child, Cryptosporidiosis, epidemiology, transmission, Cryptosporidium, isolation & purification, Diarrhea, parasitology, Disease Outbreaks, Female, Gastrointestinal Diseases, Humans, Male, Middle Aged, Seasons, Urban Health, Water Supply, Wisconsin

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          Abstract

          Early in the spring of 1993 there was a widespread outbreak of acute watery diarrhea among the residents of Milwaukee. We investigated the two Milwaukee water-treatment plants, gathered data from clinical laboratories on the results of tests for enteric pathogens, and examined ice made during the time of the outbreak for cryptosporidium oocysts. We surveyed residents with confirmed cryptosporidium infection and a sample of those with acute watery diarrhea consistent with cryptosporidium infection. To estimate the magnitude of the outbreak, we also conducted a survey using randomly selected telephone numbers in Milwaukee and four surrounding counties. There were marked increases in the turbidity of treated water at the city's southern water-treatment plant from March 23 until April 9, when the plant was shut down. Cryptosporidium oocysts were identified in water from ice made in southern Milwaukee during these weeks. The rates of isolation of other enteric pathogens remained stable, but there was more than a 100-fold increase in the rate of isolation of cryptosporidium. The median duration of illness was 9 days (range, 1 to 55). The median maximal number of stools per day was 12 (range, 1 to 90). Among 285 people surveyed who had laboratory-confirmed cryptosporidiosis, the clinical manifestations included watery diarrhea (in 93 percent), abdominal cramps (in 84 percent), fever (in 57 percent), and vomiting (in 48 percent). We estimate that 403,000 people had watery diarrhea attributable to this outbreak. This massive outbreak of watery diarrhea was caused by cryptosporidium oocysts that passed through the filtration system of one of the city's water-treatment plants. Water-quality standards and the testing of patients for cryptosporidium were not adequate to detect this outbreak.

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          Large community outbreak of cryptosporidiosis due to contamination of a filtered public water supply.

          Between January 12 and February 7, 1987, an outbreak of gastroenteritis affected an estimated 13,000 people in a county of 64,900 residents in western Georgia. Cryptosporidium oocysts were identified in the stools of 58 of 147 patients with gastroenteritis (39 percent) tested during the outbreak. Studies for bacterial, viral, and other parasitic pathogens failed to implicate any other agent. In a random telephone survey, 299 of 489 household members exposed to the public water supply (61 percent) reported gastrointestinal illness, as compared with 64 of 322 (20 percent) who were not exposed (relative risk, 3.1; 95 percent confidence interval, 2.4 to 3.9). The prevalence of IgG to cryptosporidium was significantly higher among exposed respondents to the survey who had become ill than among nonresident controls. Cryptosporidium oocysts were identified in samples of treated public water with use of a monoclonal-antibody test. Although the sand-filtered and chlorinated water system met all regulatory-agency quality standards, sub-optimal flocculation and filtration probably allowed the parasite to pass into the drinking-water supply. Low-level cryptosporidium infection in cattle in the watershed and a sewage overflow were considered as possible contributors to the contamination of the surface-water supply. We conclude that current standards for the treatment of public water supplies may not prevent the contamination of drinking water by cryptosporidium, with consequent outbreaks of cryptosporidiosis.
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            Cryptosporidiosis.

            Before 1982, only eight case reports of human cryptosporidiosis and fewer than 30 papers on Cryptosporidium spp. appeared in the biomedical literature. At that time, cryptosporidiosis was thought to be an infrequent infection in animals and rarely an opportunistic infection in humans. The concept of Cryptosporidium spp. as pathogens has changed dramatically within the past 8 years because of improved diagnostic techniques, increased awareness within the biomedical community, and the development of basic research programs in numerous laboratories. Presently, greater than 1,000 publications including over 400 case reports in the biomedical literature address Cryptosporidium spp. and cryptosporidiosis. Cryptosporidium parvum is now thought to be one of the three most common enteropathogens causing diarrheal illness in humans worldwide, especially in developing countries. It is likely that cryptosporidiosis was previously included in the 25 to 35% of diarrheal illness with unknown etiology. Because of the severity and length of diarrheal illness and because no effective therapy has been identified, cryptosporidiosis is one of the most ominous infections associated with AIDS. The role of C. parvum as an enteropathogen is well established; documentation of its role as a cause of hepatobiliary and respiratory diseases is now appearing in the literature. Our present understanding of the natural history, epidemiology, biology, and immunology of Cryptosporidium spp. as well as the clinical features, pathogenicity, and treatment of cryptosporidiosis are reviewed here.
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              Human cryptosporidiosis in immunocompetent and immunodeficient persons. Studies of an outbreak and experimental transmission.

              Infection with cryptosporidium occurred in 12 immunocompetent persons who had direct contact with the feces of infected calves during three unrelated outbreaks of calf cryptosporidiosis. Nine of the twelve subjects had diarrhea and abdominal cramps that lasted 1 to 10 days. Infections were diagnosed and monitored by detection of oocysts in feces, with a modified Sheather's flotation technique and phase-contrast microscopy. Oocysts of cryptosporidium were isolated from calves but not from other animals with which these subjects had been in contact. Oocysts of cryptosporidium were also detected during repeated examinations of feces from two immunodeficient patients with persistent cryptosporidiosis. An apparently identical infection was transmitted to calves and mice, using oocysts from infected calves and human beings. Oocysts from an immunodeficient person also produced infections in kittens, puppies, and goats. This study shows that cryptosporidium may produce a moderate self-limited illness in immunocompetent persons, which contrasts sharply with the prolonged severe diarrhea in immunocompromised patients who contract cryptosporidiosis. Calves with diarrhea should be considered a potential source of human infection, and immunocompromised persons should avoid contact with such animals.
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