title: Post-infection symptoms following two large waterborne outbreaks of Cryptosporidium hominis in Northern Sweden, 2010-2011.
abstract: BACKGROUND
  In 2010-2011, two large waterborne outbreaks caused by Cryptosporidium hominis affected two cities in Sweden, Östersund and Skellefteå. We investigated potential post-infection health consequences in people who had reported symptoms compatible with cryptosporidiosis during the outbreaks using questionnaires.
  
  
  METHODS
  We compared cases linked to these outbreaks with non-cases in terms of symptoms present up to eleven months after the initial infection. We examined if cases were more likely to report a list of symptoms at follow-up than non-cases, calculating odds ratios (OR) and 95 % confidence intervals (CI) obtained through logistic regression.
  
  
  RESULTS
  A total of 872 (310 cases) and 743 (149 cases) individuals responded to the follow-up questionnaires in Östersund and Skellefteå respectively. Outbreak cases were more likely to report diarrhea (Östersund OR: 3.3, CI: 2.0-5.3. Skellefteå OR: 3.6, CI: 2.0-6.6), watery diarrhea (Östersund OR: 3.4, CI: 1.9-6.3. Skellefteå OR: 2.8, CI: 1.5-5.1) abdominal pain (Östersund OR: 2.1, CI: 1.4-3.3, Skellefteå OR: 2.7, CI: 1.5-4.6) and joint pain (Östersund OR: 2.0, CI: 1.2-3.3, Skellefteå OR: 2.0, CI: 1.1-3.6) at follow-up compared to non-cases.
  
  
  CONCLUSIONS
  Our findings suggest that gastrointestinal- and joint symptoms can persist several months after the initial infection with Cryptosporidium and should be regarded as a potential cause of unexplained symptoms in people who have suffered from the infection.
authors.affiliation: Public Health Agency of Sweden, Solna, Sweden. moa.rehn@folkhalsomyndigheten.se.|European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden. moa.rehn@folkhalsomyndigheten.se.
authors.forename: Moa
authors.initials: M
authors.lastname: Rehn
authors.affiliation: Public Health Agency of Sweden, Solna, Sweden. Anders.Wallensten@folkhalsomyndigheten.se.|Department of Medical Sciences, Infectious Diseases, Uppsala University, Uppsala, Sweden. Anders.Wallensten@folkhalsomyndigheten.se.
authors.forename: Anders
authors.initials: A
authors.lastname: Wallensten
authors.affiliation: Department of Clinical Microbiology, Unit of Communicable Disease Control and Prevention- Östersund, Umeå University, Umeå, Sweden. micael.widerstrom@regionjh.se.
authors.forename: Micael
authors.initials: M
authors.lastname: Widerström
authors.affiliation: Department of Public health and Clinical Medicine, Unit of Clinical Research Center - Östersund, Umeå University, Umeå, Sweden. mikael.lilja@regionjh.se.
authors.forename: Mikael
authors.initials: M
authors.lastname: Lilja
authors.affiliation: Public Health Agency of Sweden, Solna, Sweden. maria.grunewald@scanddev.se.
authors.forename: Maria
authors.initials: M
authors.lastname: Grunewald
authors.affiliation: Department for Infectious Disease Control, Västerbotten County Council, Umeå, Sweden. stephan.stenmark@umu.se.
authors.forename: Stephan
authors.initials: S
authors.lastname: Stenmark
authors.affiliation: Public Health Agency of Sweden, Solna, Sweden. malin.kark@folkhalsomyndigheten.se.
authors.forename: Malin
authors.initials: M
authors.lastname: Kark
authors.affiliation: Department of Cell and Molecular Biology, Microbiology, Uppsala University, Box 256, 751 05, Uppsala, Sweden. johan.lindh@icm.uu.se.
authors.forename: Johan
authors.initials: J
authors.lastname: Lindh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D018771:Arthralgia / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D003457:Cryptosporidiosis / Q000150:complications* / Q000453:epidemiology*; D003458:Cryptosporidium; D003967:Diarrhea / Q000453:epidemiology*; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult