Routes of transmission during a nosocomial influenza A(H3N2) outbreak among geriatric patients and healthcare workers.
BACKGROUND
Influenza presents a life-threatening infection for hospitalized geriatric patients, who might be nosocomially infected via healthcare workers (HCWs), other patients or visitors. In the 2011/2012 influenza season an influenza A(H3N2) outbreak occurred in the geriatric department at the Hôpital Edouard Herriot, Lyon.


OBJECTIVE
To clarify the transmission chain for this influenza A(H3N2) outbreak by sequence analysis and to identify preventive measures.


METHODS
Laboratory testing of patients with influenza-like illness in the acute care geriatric department revealed 22 cases of influenza between 19th February and 15th March 2012. Incidences for patients and HCWs were calculated and possible epidemiological links were analysed using a questionnaire. Neuraminidase and haemagglutinin genes of culture-positive samples and community influenza samples were sequenced and clustered to detect patients with identical viral strains.


RESULTS
Sixteen patients and six HCWs were affected, resulting in an attack rate of 24% and 11% respectively. Six nosocomial infections were recorded. The sequence analysis confirmed three independent influenza clusters on three different sections of the geriatric ward. For at least two clusters, an HCW source was determined.


CONCLUSIONS
Epidemiological and microbiological results confirm influenza transmission from HCWs to patients. A higher vaccination rate, isolation measures and better hand hygiene are recommended in order to prevent outbreaks in future influenza seasons.
Virology Department, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, Lyon, France; European Public Health Microbiology Training Programme (EUPHEM), European Centre for Disease Prevention and Control, Stockholm, Sweden. Electronic address: daniel.eibach@chu-lyon.fr.
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D
Eibach
Virology Department, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, Lyon, France.
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JS
Casalegno
Virology Department, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, Lyon, France.
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M
Bouscambert
Infection Control and Epidemiology Unit, Edouard Herriot Hospital, Hospices Civils de Lyon, Lyon, France; Epidemiology and Public Health Group, CNRS UMR 5558, University of Lyon 1, Lyon, France.
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T
Bénet
Infection Control and Epidemiology Unit, Edouard Herriot Hospital, Hospices Civils de Lyon, Lyon, France; Epidemiology and Public Health Group, CNRS UMR 5558, University of Lyon 1, Lyon, France.
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C
Regis
PAM de gériatrie, Edouard Herriot Hospital, Hospices Civils de Lyon, Lyon, France.
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B
Comte
PAM de gériatrie, Edouard Herriot Hospital, Hospices Civils de Lyon, Lyon, France.
B-A
BA
Kim
Infection Control and Epidemiology Unit, Edouard Herriot Hospital, Hospices Civils de Lyon, Lyon, France; Epidemiology and Public Health Group, CNRS UMR 5558, University of Lyon 1, Lyon, France.
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P
Vanhems
Virology Department, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, Lyon, France.
B
B
Lina
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016000:Cluster Analysis; D003428:Cross Infection / Q000453:epidemiology* / Q000635:transmission*; D004196:Disease Outbreaks; D005260:Female; D005602:France / Q000453:epidemiology; D005838:Genotype; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000635:transmission*; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D009439:Neuraminidase / Q000235:genetics; D010802:Phylogeny; D012367:RNA, Viral / Q000235:genetics; D017422:Sequence Analysis, DNA; D011795:Surveys and Questionnaires; D014764:Viral Proteins / Q000235:genetics; D055815:Young Adult
D019267:Hemagglutinin Glycoproteins, Influenza Virus; D012367:RNA, Viral; D014764:Viral Proteins; C487630:NA protein, influenza A virus; D009439:Neuraminidase
Healthcare worker; Influenza; Nosocomial infection; Outbreak