title: Influence of observable and unobservable exposure on the patient's risk of acquiring influenza-like illness at hospital.
abstract: During outbreaks of hospital-acquired influenza-like illness (HA-ILI) healthcare workers (HCWs), patients, and visitors are each a source of infection for the other. Quantifying the effects of these various exposures will help improve prevention and control of HA-ILI outbreaks. We estimated the attributability of HA-ILI to: (1) exposure to recorded or unrecorded sources; (2) exposure to contagious patient or contagious HCW; (3) exposure during observable or unobservable contagious period of the recorded sources; and, (4) the moment of exposure. Among recorded sources, 59% [95% credible interval (CrI) 34-83] of HA-ILI of patients was associated with exposure to contagious patients and 41% (95% CrI 17-66) with exposure to contagious HCWs. Exposure during the unobservable contagiousness period of source patients accounted for 49% (95% CrI 19-75) of HA-ILI, while exposure during the unobservable contagiousness period of source HCWs accounted for 82% (95% CrI 51-99) of HA-ILI. About 80% of HA-ILIs were associated with exposure 1 day earlier. Secondary cases of HA-ILI might appear as soon as the day after the detection of a primary case highlighting the explosive nature of HA-ILI spread. Unobservable transmission was the main cause of HA-ILI transmission suggesting that symptom-based control measures alone might not prevent hospital outbreaks. The results support the rapid implementation of interventions to control influenza transmission.
authors: Hospices Civils de Lyon, Service d'Hygiène, Epidémiologie et Prévention,Unité Epidémiologie et Biomarqueurs de l'Infection,Lyon,France.
authors: C
authors: C
authors: Payet
authors: Hospices Civils de Lyon, Service d'Hygiène, Epidémiologie et Prévention,Unité Epidémiologie et Biomarqueurs de l'Infection,Lyon,France.
authors: N
authors: N
authors: Voirin
authors: Université de Lyon,Lyon,France.
authors: R
authors: R
authors: Ecochard
authors: Hospices Civils de Lyon, Service d'Hygiène, Epidémiologie et Prévention,Unité Epidémiologie et Biomarqueurs de l'Infection,Lyon,France.
authors: P
authors: P
authors: Vanhems
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003428:Cross Infection / Q000453:epidemiology* / Q000635:transmission; D004196:Disease Outbreaks; D005260:Female; D005602:France / Q000453:epidemiology; D006282:Health Personnel; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology* / Q000635:transmission; D007297:Inpatients; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012306:Risk; D055815:Young Adult
keywords: Cross-infections; epidemiology; hospitals; infection transmission; influenza; statistical model