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Transmission of influenza virus from asymptomatic healthcare workers and inpatients in the acute care hospital setting: A prospective study over two consecutive influenza seasons

English title Transmission of influenza virus from asymptomatic healthcare workers and inpatients in the acute care hospital setting: A prospective study over two consecutive influenza seasons
Applicant Kuster Stefan
Number 156902
Funding scheme Project funding (Div. I-III)
Research institution Abteilung für Infektionskrankheiten Medizinische Poliklinik Universitätsspital Zürich
Institution of higher education University of Zurich - ZH
Main discipline Infectious Diseases
Start/End 01.05.2015 - 30.04.2019
Approved amount 469'196.00
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All Disciplines (2)

Discipline
Infectious Diseases
Methods of Epidemiology and Preventive Medicine

Keywords (6)

transmission; asymptomatic; influenza; health care worker; acute care hospital; secondary attack rate

Lay Summary (German)

Lead
Nach wie vor ist unklar, ob Influenza (Grippe) durch asymptomatische Personen übertragen werden kann. Das vorliegende Projekt untersucht die Frage, ob Personen ohne Symptome wie Husten, Schnupfen, Fieber, Heiserkeit und Halsschmerzen in der Lage sind, Influenza auf andere Personen im Akutspital zu übertragen.
Lay summary

Projekttitel

Die Übertragung von Influenza (Grippe) zwischen asymptomatischen Spitalangestellten und hospitalisierten Patienten im Akutspital: eine prospektive Studie über zwei aufeinanderfolgende Influenzasaisons

Hintergrund

Die Epidemiologie und Transmissionsdynamik des Grippevirus in Spitälern sind nur wenig erforscht, speziell in Bezug auf Personen, welche noch keine Krankheitssymptome aufweisen. Die Frage, ob asymptomatische Personen in der Lage sind, Influenza zu übertragen, ist nach wie vor ungelöst. Experimentelle Studien zeigen zwar, dass das Influenzavirus bereits vor Auftreten von Symptomen über die Nasenschleimhäute ausgeschieden wird, allerdings ist unklar, ob die Ausscheidung von Virus in dieser Menge und ohne Symptome (speziell Husten und Schnupfen) ausreicht, das Virus von Person zu Person zu übertragen. Die Schliessung dieser Wissenslücke ist wichtig, um präventive Massnahmen (z.B. Grippeimpfung, Tragen von Masken bei Krankheitssymptomen) in Spitälern  gezielt und evidenzbasiert vorantreiben zu können.

Inhalt und Ziele des Forschungsprojekts

Mit der vorliegenden Studie wird mittels aktiver Surveillance die Frage untersucht, ob asymptomatische Personen in der Spitalumgebung in der Lage sind, Influenza auf andere Personen zu übertragen. Es kommen epidemiologische, molekularbiologische und phylogenetische Methoden zum Einsatz. Beim Vergleich der Grippeviren von verschiedenen Personen lässt sich die Wahrscheinlichkeit abschätzen, ob eine direkte Übertragung von Person zu Person im Spital stattgefunden hat.

Bedeutung

Die Resultate der Studie werden einen wichtigen Beitrag zum Verständnis der Influenzatransmission in der Spitalumgebung und zur Erhöhung der Patientensicherheit leisten, indem präventive Massnahmen wie Grippeimpfung und Distanzhalten gezielter eingesetzt werden können.

Direct link to Lay Summary Last update: 16.12.2014

Responsible applicant and co-applicants

Employees

Publications

Publication
The TransFLUas influenza transmission study in acute healthcare - recruitment rates and protocol adherence in healthcare workers and inpatients
Schwarz Hila, Böni Jürg, Kouyos Roger D., Turk Teja, Battegay Edouard, Kohler Malcolm, Müller Rouven, Petry Heidi, Sax Hugo, Weber Rainer, McGeer Allison, Trkola Alexandra, Kuster Stefan P. (2019), The TransFLUas influenza transmission study in acute healthcare - recruitment rates and protocol adherence in healthcare workers and inpatients, in BMC Infectious Diseases, 19(1), 446-446.
Influence of time to diagnosis of severe influenza on antibiotic use, length of stay, isolation precautions, and mortality: a retrospective study
Akers Isabel E., Weber Rainer, Sax Hugo, Böni Jürg, Trkola Alexandra, Kuster Stefan P. (2017), Influence of time to diagnosis of severe influenza on antibiotic use, length of stay, isolation precautions, and mortality: a retrospective study, in Influenza and Other Respiratory Viruses, 11(4), 337-344.

Collaboration

Group / person Country
Types of collaboration
Prof. Edward C. Holmes, School of Life and Environmental Sciences and Sydney Medical School, Sydney Australia (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
Prof. Allison McGeer, Department of Microbiology, Sinai Health System, Toronto Canada (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
29th European Congress of Clinical Microbiology & Infectious Diseases Talk given at a conference The TransFLUas influenza transmission study in acute healthcare: attack rates, symptoms and transmission clusters 13.04.2019 Amsterdam, Netherlands Tamo Raphael; Trkola Alexandra; Kuster Stefan;


Communication with the public

Communication Title Media Place Year
Media relations: print media, online media Hospital study finds substantial proportion of patients and healthcare workers shed flu virus before ECCMID media release International 2019

Associated projects

Number Title Start Funding scheme
172790 Understanding HIV-1 broadly neutralizing antibody evolution - The Swiss 4.5K Screen 01.04.2017 Project funding (special)

Abstract

The epidemiology and transmission dynamics of influenza in hospitals are only poorly understood, particularly with respect to subjects without symptoms of influenza infection (e.g. without fever, cough, sore throat, nasal congestion, weakness, headache, loss of appetite, or myalgia). Knowledge about whether asymptomatic subjects are able to transmit influenza is of major importance. If they do transmit influenza, vaccination of patients and healthcare workers (HCW) before start of the influenza season, the permanent use of masks by HCW during influenza season, and quarantine for previously exposed inpatients may be the only available measures to reduce the number of influenza transmission events from asymptomatic subjects in acute care hospitals. Closure of this knowledge gap would be of major benefit to infection prevention and control recommendations, and may in turn reduce morbidity and mortality associated with influenza in hospitals through improved patient management.Our key aim is therefore to define whether exposure to asymptomatic subjects with influenza infection constitutes a risk for influenza transmission in an acute care hospital setting through active, prospective surveillance. Our secondary aims are to describe the prevalence of community-acquired symptomatic and asymptomatic influenza upon hospital admission and the incidence of asymptomatic and symptomatic nosocomial influenza among inpatients; to assess transmission dynamics of symptomatic influenza infection in acute care; and to study the incidence of asymptomatic and symptomatic influenza, absenteeism (i.e. being absent from work due to influenza), presenteeism (i.e. being present at work despite influenza infection) associated with influenza, and compliance with infection control recommendations to prevent spread of influenza in acute care HCW. Based on our sample size calculations, we plan to enroll 1,260 inpatients and 180 HCW from medical wards at the University Hospital Zurich in a prospective study over two consecutive influenza seasons in order to detect at least one transmission event from an asymptomatic individual shedding influenza virus. Flocked mid-turbinate nasal swabs will be collected daily from consenting inpatients starting from day of admission until two days after discharge and from HCW over the influenza (winter) season and analyzed for influenza A and B using polymerase chain reaction. Simultaneously, signs and symptoms of influenza infection (including cough, sore throat, fever >37.8°C, nasal congestion, weakness, headache, loss of appetite or myalgia) as well as contact patterns between inpatients and HCW will be recorded. Reconstruction of influenza transmission chains will be based on phylogenetic analyses derived from next-generation sequence data and epidemiological contact tracing. We are confident that the results of our study will assist policy makers and clinicians with decisions regarding better implementation of other potential preventive measures against influenza transmission in hospitals.
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