Secondary attack rates from asymptomatic and symptomatic influenza virus shedders in hospitals: Results from the TransFLUas influenza transmission study.
Infect Control Hosp Epidemiol
; 43(3): 312-318, 2022 03.
Article
in En
| MEDLINE
| ID: mdl-33952361
ABSTRACT
OBJECTIVE:
Nosocomial transmission of influenza is a major concern for infection control. We aimed to dissect transmission dynamics of influenza, including asymptomatic transmission events, in acute care.DESIGN:
Prospective surveillance study during 2 influenza seasons.SETTING:
Tertiary-care hospital.PARTICIPANTS:
Volunteer sample of inpatients on medical wards and healthcare workers (HCWs).METHODS:
Participants provided daily illness diaries and nasal swabs for influenza A and B detection and whole-genome sequencing for phylogenetic analyses. Contacts between study participants were tracked. Secondary influenza attack rates were calculated based on spatial and temporal proximity and phylogenetic evidence for transmission.RESULTS:
In total, 152 HCWs and 542 inpatients were included; 16 HCWs (10.5%) and 19 inpatients (3.5%) tested positive for influenza on 109 study days. Study participants had symptoms of disease on most of the days they tested positive for influenza (83.1% and 91.9% for HCWs and inpatients, respectively). Also, 11(15.5%) of 71 influenza-positive swabs among HCWs and 3 (7.9%) of 38 influenza-positive swabs among inpatients were collected on days without symptoms; 2 (12.5%) of 16 HCWs and 2 (10.5%) of 19 inpatients remained fully asymptomatic. The secondary attack rate was low we recorded 1 transmission event over 159 contact days (0.6%) that originated from a symptomatic case. No transmission event occurred in 61 monitored days of contacts with asymptomatic influenza-positive individuals.CONCLUSIONS:
Influenza in acute care is common, and individuals regularly shed influenza virus without harboring symptoms. Nevertheless, both symptomatic and asymptomatic transmission events proved rare. We suggest that healthcare-associated influenza prevention strategies that are based on preseason vaccination and barrier precautions for symptomatic individuals seem to be effective.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Orthomyxoviridae
/
Influenza, Human
Type of study:
Diagnostic_studies
/
Incidence_studies
/
Observational_studies
/
Prognostic_studies
Limits:
Humans
Language:
En
Journal:
Infect Control Hosp Epidemiol
Journal subject:
DOENCAS TRANSMISSIVEIS
/
ENFERMAGEM
/
EPIDEMIOLOGIA
/
HOSPITAIS
Year:
2022
Document type:
Article
Affiliation country:
Switzerland