title: Incidence of Hospital Norovirus Outbreaks and Infections Using 2 Surveillance Methods in Sweden.
abstract: OBJECTIVE To evaluate 2 different methods of surveillance and to estimate the incidence of norovirus (NoV) outbreaks in hospitals. DESIGN Prospective observational study. SETTING All 194 hospital wards in southern Sweden during 2 winter seasons (2010-2012). METHODS Clinical surveillance based on outbreak reports of 2 or more clinical cases, with symptom onset within 5 days, was compared with laboratory surveillance based on positive NoV results among inpatients. At least 2 NoV positive patients sampled within 5 days at a ward defined a cluster. Outbreak reports including at least 1 NoV positive case and clusters including at least 1 NoV positive patient with 5 or more days from ward admission to sampling were defined as NoV outbreaks. RESULTS During the study periods 135 NoV outbreaks were identified; 74 were identified by both clinical and laboratory surveillance, 18 were identified only by outbreak reports, and 43 were identified only by laboratory surveillance. The outbreak incidence was 1.0 (95% CI, 0.8-1.2) and 0.5 (95% CI, 0.3-0.6) per 1,000 admissions for the 2 different seasons, respectively. To correctly identify NoV outbreaks, the sensitivity and positive predictive value of the clinical surveillance were 68% and 88% and of the laboratory surveillance were 86% and 81%, respectively. CONCLUSION The addition of laboratory surveillance significantly improves outbreak surveillance and provides a more complete estimate of NoV outbreaks in hospitals. Laboratory surveillance can be recommended for evaluation of clinical surveillance. Infect Control Hosp Epidemiol 2016;1-7.
authors.affiliation: 1Department of Infection Control,Region Skåne,Lund,Sweden.
authors.forename: Carl-Johan
authors.initials: CJ
authors.lastname: Fraenkel
authors.affiliation: 2Department of Clinical Sciences,Section for Infection Medicine,Lund University,Lund,Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Inghammar
authors.affiliation: 1Department of Infection Control,Region Skåne,Lund,Sweden.
authors.forename: P J Hugo
authors.initials: PJ
authors.lastname: Johansson
authors.affiliation: 3Clinical Microbiology,University and Regional Laboratories, Region Skåne,Lund,Sweden.
authors.forename: Blenda
authors.initials: B
authors.lastname: Böttiger
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017250:Caliciviridae Infections / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D062665:Epidemiological Monitoring; D005260:Female; D005759:Gastroenteritis / Q000453:epidemiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D029322:Norovirus / Q000235:genetics; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012621:Seasons; D012680:Sensitivity and Specificity; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult