title: Endemic cryptosporidiosis and exposure to municipal tap water in persons with acquired immunodeficiency syndrome (AIDS): a case-control study.
abstract: BACKGROUND
  In persons with acquired immunodeficiency syndrome (AIDS), Cryptosporidium parvum causes a prolonged, severe diarrheal illness to which there is no effective treatment, and the risk of developing cryptosporidiosis from drinking tap water in non-outbreak settings remains uncertain. To test the hypothesis that drinking tap water was associated with developing cryptosporidiosis, we conducted a matched case-control study among persons with AIDS in San Francisco.
  
  
  METHODS
  Among patients reported to the San Francisco AIDS Registry from May 1996 through September 1998, we compared patients who developed cryptosporidiosis to those who did not. Cases were individually matched to controls based on age, sex, race/ethnicity, CD4+ T lymphocyte count, date of CD4+ count, and date of case diagnosis. Population attributable fractions (PAFs) were calculated.
  
  
  RESULTS
  The study consisted of 49 cases and 99 matched controls. In the multivariable analysis with adjustments for confounders, tap water consumption inside and outside the home at the highest exposure categories was associated with the occurrence of cryptosporidiosis (inside the home: odds ratio (OR), 6.76; 95% CI 1.37-33.5, and outside the home: OR 3.16; 95% CI 1.23-8.13). The PAF was 85%; that is, the proportion of cases of cryptosporidiosis in San Francisco AIDS patients attributable to tap water consumption could have been as high as 85%.
  
  
  CONCLUSIONS
  Although the results from this observational study cannot be considered definitive, until there is more data, we recommend persons with AIDS, especially those with compromised immune systems, consider avoiding tap water.
authors.affiliation: Department of Epidemiology and Biostatistics, and of Medicine, University of California, San Francisco, USA. aragon@itsa.ucsf.edu
authors.forename: Tomás J
authors.initials: TJ
authors.lastname: Aragón
authors.forename: Suzanne
authors.initials: S
authors.lastname: Novotny
authors.forename: Wayne
authors.initials: W
authors.lastname: Enanoria
authors.forename: Duc J
authors.initials: DJ
authors.lastname: Vugia
authors.forename: Asheena
authors.initials: A
authors.lastname: Khalakdina
authors.forename: Mitchell H
authors.initials: MH
authors.lastname: Katz
mesh_terms: D017088:AIDS-Related Opportunistic Infections / Q000276:immunology / Q000469:parasitology; D000163:Acquired Immunodeficiency Syndrome / Q000276:immunology*; D000328:Adult; D000818:Animals; D018791:CD4 Lymphocyte Count; D016022:Case-Control Studies; D003457:Cryptosporidiosis / Q000453:epidemiology* / Q000209:etiology; D016785:Cryptosporidium parvum / Q000302:isolation & purification / Q000469:parasitology*; D019353:Endemic Diseases; D005260:Female; D005374:Filtration; D006801:Humans; D016867:Immunocompromised Host; D008297:Male; D008875:Middle Aged; D012495:San Francisco / Q000453:epidemiology; D014867:Water / Q000469:parasitology*; D014876:Water Pollution / Q000032:analysis; D014881:Water Supply / Q000032:analysis / Q000592:standards*
chemical_list: D014867:Water