Clinical and epidemiologic features of a massive waterborne outbreak of cryptosporidiosis in persons with HIV infection.

During March and April 1993, a massive outbreak of Cryptosporidium infection resulted from contamination of the public water supply in Milwaukee, Wisconsin. The health impact of this outbreak in HIV-infected persons was unknown but was perceived as severe. We surveyed HIV-infected persons who resided in the greater Milwaukee area to examine the acute health impact of cryptosporidiosis on this population. Data from a random-digit dialing survey in the general population residing in the same area were used for comparison. The attack rate of watery diarrhea suggestive of cryptosporidiosis was lower in HIV-infected persons (32%) than in the general population (51%). There was no significant difference in attack rate in HIV-infected persons based on CD4+ T-lymphocyte count. In persons with watery diarrhea, HIV-infected persons were more likely to experience cough (42%), fever (52%), and dehydration (55%). In HIV-infected persons with watery diarrhea, persons with CD4+ T-lymphocyte counts <200/microl had longer duration of diarrhea and were more likely to seek medical attention and be hospitalized. During this massive waterborne outbreak, HIV-infected persons were not more likely to experience symptomatic Cryptosporidium infection than the general population. However, once infected, the duration and severity of illness was greater in HIV-infected persons, especially if the CD4+ T-lymphocyte count was <200/microl.