title: Outbreak of Cryptosporidium hominis following river flooding in the city of Halle (Saale), Germany, August 2013.
abstract: BACKGROUND
  During weeks 32-33, 2013, 24 cases of cryptosporidiosis were notified in the city of Halle (annual mean 2008-2012: 9 cases). We investigated the outbreak to identify the source and recommend control measures, considering that between weeks 23-25 the river Saale which flows through the city centre overflowed the floodplain, parts of the city centre and damaged sewage systems.
  
  
  METHODS
  We defined a case as a resident of Halle with gastroenteritis, Cryptosporidium-positive stool and disease onset weeks 27 through 47. In a case-control study among kindergarten children, we compared cases and controls regarding environmental exposure, use of swimming pools, zoo visits and tap water consumption 14 days pre-onset or a corresponding 14-days-period (controls) and adjusted for residence. Stool specimens were tested by microscopy and PCR, and Cryptosporidium DNA was sequenced. Samples from public water system, swimming pools and river Saale were examined for Cryptosporidium oocysts (microscopy and PCR).
  
  
  RESULTS
  Overall, 167 cases were detected, 40/167 (24%) were classified as secondary cases. First disease onsets occurred during week 29, numbers peaked in week 34 and started to decrease in week 36. Median age was 8 years (range: 0-77). Compared to controls (n = 61), cases (n = 20) were more likely to report visits to previously flooded areas (OR: 4.9; 95%-CI: 1.4-18) and the zoo (OR: 2.6; 95%-CI: 0.9-7.6). In multivariable analysis visits to the floodplain remained the sole risk factor (OR: 5.5; 95%-CI: 1.4-22). Only C.hominis of a single genotype (IbA9G2) was detected in stools. Oocysts were detected in samples from the river, two local lakes and three public swimming pools by microscopy, but not in the public water supply.
  
  
  CONCLUSIONS
  Evidence suggests that activities in the dried out floodplain led to infection among children. Secondary transmissions may be involved. Consequently, authorities recommended to avoid playing, swimming and having picnics in the flood-affected area. Health authorities should consider the potential health risks of long-term surviving parasites persisting on flooded grounds and in open waters even several weeks after the flooding and of bathing places close to sewage spill-overs. Preventive measures comprise water sampling (involving parasites), information of the public and prolonged closures of potentially contaminated sites.
authors: Department for Infectious Disease Epidemiology, Robert Koch Institute (RKI), Seestraße 10, 13353, Berlin, Germany. mgertler@gmx.de.|Postgraduate Training for Applied Epidemiology, affiliated to the European Programme for Intervention Epidemiology Training, European Centres of Disease Controle (ECDC), Sweden, Europe. mgertler@gmx.de.
authors: Maximilian
authors: M
authors: Gertler
authors: Public Health authority Halle (Saale), Niemeyerstraße 1, 06110, Halle (Saale), Germany. Matthias.Duerr@halle.de.
authors: Matthias
authors: M
authors: Dürr
authors: Federal Environment Protection Agency (UBA), Heinrich-Heine-Str. 12, 08645, Bad Elster, Germany. peter.renner@uba.de.
authors: Peter
authors: P
authors: Renner
authors: National Reference Centre for Tropical Pathogens, Bernhard Nocht Institute for Tropical Medicine (BNI), Bernhard-Nocht-Straße 74, 20359, Hamburg, Germany. sven@poppert.eu.|Justus-Liebig-University Giessen, Institute of Medical Microbiology, Giessen, Germany. sven@poppert.eu.
authors: Sven
authors: S
authors: Poppert
authors: Department for Infectious Disease Epidemiology, Robert Koch Institute (RKI), Seestraße 10, 13353, Berlin, Germany. AskarM@rki.de.
authors: Mona
authors: M
authors: Askar
authors: Department for Infectious Disease Epidemiology, Robert Koch Institute (RKI), Seestraße 10, 13353, Berlin, Germany. BreidenbachJ@rki.de.
authors: Janina
authors: J
authors: Breidenbach
authors: Department for Infectious Disease Epidemiology, Robert Koch Institute (RKI), Seestraße 10, 13353, Berlin, Germany. FrankC@rki.de.
authors: Christina
authors: C
authors: Frank
authors: Department for Infectious Disease Epidemiology, Robert Koch Institute (RKI), Seestraße 10, 13353, Berlin, Germany. PreusselK@rki.de.
authors: Karina
authors: K
authors: Preußel
authors: Department for Infectious Disease Epidemiology, Robert Koch Institute (RKI), Seestraße 10, 13353, Berlin, Germany. SchielkeA@rki.de.
authors: Anika
authors: A
authors: Schielke
authors: Department for Infectious Disease Epidemiology, Robert Koch Institute (RKI), Seestraße 10, 13353, Berlin, Germany. Dirk.Werber@lageso.de.
authors: Dirk
authors: D
authors: Werber
authors: Cryptosporidium Reference Unit, Public Health Wales Microbiology, Singleton Hospital, Swansea, SA2 8QA, UK. Rachel.Chalmers@wales.nhs.uk.
authors: Rachel
authors: R
authors: Chalmers
authors: Cryptosporidium Reference Unit, Public Health Wales Microbiology, Singleton Hospital, Swansea, SA2 8QA, UK. guy.robinson@wales.nhs.uk.
authors: Guy
authors: G
authors: Robinson
authors: Federal Environment Protection Agency (UBA), Heinrich-Heine-Str. 12, 08645, Bad Elster, Germany. irmgard.feuerpfeil@uba.de.
authors: Irmgard
authors: I
authors: Feuerpfeil
authors: National Reference Centre for Tropical Pathogens, Bernhard Nocht Institute for Tropical Medicine (BNI), Bernhard-Nocht-Straße 74, 20359, Hamburg, Germany. tannich@bni-hamburg.de.
authors: Egbert
authors: E
authors: Tannich
authors: Public Health authority Halle (Saale), Niemeyerstraße 1, 06110, Halle (Saale), Germany. Christine.groeger@halle.de.
authors: Christine
authors: C
authors: Gröger
authors: Department for Infectious Disease Epidemiology, Robert Koch Institute (RKI), Seestraße 10, 13353, Berlin, Germany. StarkK@rki.de.
authors: Klaus
authors: K
authors: Stark
authors: Department for Infectious Disease Epidemiology, Robert Koch Institute (RKI), Seestraße 10, 13353, Berlin, Germany. WilkingH@rki.de.
authors: Hendrik
authors: H
authors: Wilking
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003457:Cryptosporidiosis / Q000453:epidemiology* / Q000469:parasitology; D003458:Cryptosporidium / Q000302:isolation & purification; D004196:Disease Outbreaks; D005260:Female; D055868:Floods / Q000706:statistics & numerical data; D005759:Gastroenteritis / Q000453:epidemiology / Q000469:parasitology; D005858:Germany / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D045483:Rivers / Q000469:parasitology; D013551:Swimming Pools; D014881:Water Supply; D055815:Young Adult