title: Laboratory-based prospective surveillance for community outbreaks of Shigella spp. in Argentina.
abstract: BACKGROUND
  To implement effective control measures, timely outbreak detection is essential. Shigella is the most common cause of bacterial diarrhea in Argentina. Highly resistant clones of Shigella have emerged, and outbreaks have been recognized in closed settings and in whole communities. We hereby report our experience with an evolving, integrated, laboratory-based, near real-time surveillance system operating in six contiguous provinces of Argentina during April 2009 to March 2012.
  
  
  METHODS
  To detect localized shigellosis outbreaks timely, we used the prospective space-time permutation scan statistic algorithm of SaTScan, embedded in WHONET software. Twenty three laboratories sent updated Shigella data on a weekly basis to the National Reference Laboratory. Cluster detection analysis was performed at several taxonomic levels: for all Shigella spp., for serotypes within species and for antimicrobial resistance phenotypes within species. Shigella isolates associated with statistically significant signals (clusters in time/space with recurrence interval ≥365 days) were subtyped by pulsed field gel electrophoresis (PFGE) using PulseNet protocols.
  
  
  RESULTS
  In three years of active surveillance, our system detected 32 statistically significant events, 26 of them identified before hospital staff was aware of any unexpected increase in the number of Shigella isolates. Twenty-six signals were investigated by PFGE, which confirmed a close relationship among the isolates for 22 events (84.6%). Seven events were investigated epidemiologically, which revealed links among the patients. Seventeen events were found at the resistance profile level. The system detected events of public health importance: infrequent resistance profiles, long-lasting and/or re-emergent clusters and events important for their duration or size, which were reported to local public health authorities.
  
  
  CONCLUSIONS
  The WHONET-SaTScan system may serve as a model for surveillance and can be applied to other pathogens, implemented by other networks, and scaled up to national and international levels for early detection and control of outbreaks.
authors.affiliation: Departamento Bacteriología, Instituto Nacional de Enfermedades Infecciosas ANLIS "Dr C. G. Malbrán", Buenos Aires, Argentina.
authors.forename: María R
authors.initials: MR
authors.lastname: Viñas
authors.affiliation: Departamento Bacteriología, Instituto Nacional de Enfermedades Infecciosas ANLIS "Dr C. G. Malbrán", Buenos Aires, Argentina.
authors.forename: Ezequiel
authors.initials: E
authors.lastname: Tuduri
authors.affiliation: Department of Medicine, Brigham and Women's Hospital, World Health Organization Collaborating Centre for Surveillance of Antimicrobial Resistance, Boston, Massachusetts, United States of America.
authors.forename: Alicia
authors.initials: A
authors.lastname: Galar
authors.affiliation: Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, Massachusetts, United States of America.
authors.forename: Katherine
authors.initials: K
authors.lastname: Yih
authors.affiliation: Departamento Bacteriología, Instituto Nacional de Enfermedades Infecciosas ANLIS "Dr C. G. Malbrán", Buenos Aires, Argentina.
authors.forename: Mariana
authors.initials: M
authors.lastname: Pichel
authors.affiliation: Department of Medicine, Brigham and Women's Hospital, World Health Organization Collaborating Centre for Surveillance of Antimicrobial Resistance, Boston, Massachusetts, United States of America.
authors.forename: John
authors.initials: J
authors.lastname: Stelling
authors.affiliation: Departamento Bacteriología, Instituto Nacional de Enfermedades Infecciosas ANLIS "Dr C. G. Malbrán", Buenos Aires, Argentina.
authors.forename: Silvina P
authors.initials: SP
authors.lastname: Brengi
authors.affiliation: Departamento Bacteriología, Instituto Nacional de Enfermedades Infecciosas ANLIS "Dr C. G. Malbrán", Buenos Aires, Argentina.
authors.forename: Anabella
authors.initials: A
authors.lastname: Della Gaspera
authors.affiliation: Servicio de Antígenos y Antisueros. Instituto Nacional de Producción de Biológicos (INPB) - ANLIS "Dr Carlos G. Malbran", Buenos Aires, Argentina.
authors.forename: Claudia
authors.initials: C
authors.lastname: van der Ploeg
authors.affiliation: Servicio de Antígenos y Antisueros. Instituto Nacional de Producción de Biológicos (INPB) - ANLIS "Dr Carlos G. Malbran", Buenos Aires, Argentina.
authors.forename: Susana
authors.initials: S
authors.lastname: Bruno
authors.affiliation: Servicio de Antígenos y Antisueros. Instituto Nacional de Producción de Biológicos (INPB) - ANLIS "Dr Carlos G. Malbran", Buenos Aires, Argentina.
authors.forename: Ariel
authors.initials: A
authors.lastname: Rogé
authors.affiliation: Departamento Bacteriología, Instituto Nacional de Enfermedades Infecciosas ANLIS "Dr C. G. Malbrán", Buenos Aires, Argentina.
authors.forename: María I
authors.initials: MI
authors.lastname: Caffer
authors.affiliation: Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, Massachusetts, United States of America.
authors.forename: Martin
authors.initials: M
authors.lastname: Kulldorff
authors.affiliation: Departamento Bacteriología, Instituto Nacional de Enfermedades Infecciosas ANLIS "Dr C. G. Malbrán", Buenos Aires, Argentina.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Galas
mesh_terms: D001118:Argentina / Q000453:epidemiology; D016000:Cluster Analysis; D004196:Disease Outbreaks; D004405:Dysentery, Bacillary / Q000453:epidemiology*; D016521:Electrophoresis, Gel, Pulsed-Field; D062665:Epidemiological Monitoring; D006801:Humans; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D012703:Serotyping; D012760:Shigella / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*