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Segregation of virulent influenza A(H1N1) variants in the lower respiratory tract of critically ill patients during the 2010-2011 seasonal epidemic.

ABSTRACT: BACKGROUND: Since its appearance in 2009, the pandemic influenza A(H1N1) virus circulated worldwide causing several severe infections. METHODS: Respiratory samples from patients with 2009 influenza A(H1N1) and acute respiratory distress attending 24 intensive care units (ICUs) as well as from patients with lower respiratory tract infections not requiring ICU admission and community upper respiratory tract infections in the Lombardy region (10 million inhabitants) of Italy during the 2010-2011 winter-spring season, were analyzed. RESULTS: In patients with severe ILI, the viral load was higher in bronchoalveolar lavage (BAL) with respect to nasal swab (NS), (p<0.001) suggesting a higher virus replication in the lower respiratory tract. Four distinct virus clusters (referred to as cluster A to D) circulated simultaneously. Most (72.7%, n?=?48) of the 66 patients infected with viruses belonging to cluster A had a severe (n?=?26) or moderate ILI (n?=?22). Amino acid mutations (V26I, I116M, A186T, D187Y, D222G/N, M257I, S263F, I286L/M, and N473D) were observed only in patients with severe ILI. D222G/N variants were detected exclusively in BAL samples. CONCLUSIONS: Multiple virus clusters co-circulated during the 2010-2011 winter-spring season. Severe or moderate ILI were associated with specific 2009 influenza A(H1N1) variants, which replicated preferentially in the lower respiratory tract.

SUBMITTER: Piralla A

PROVIDER: S-EPMC3237448 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Segregation of virulent influenza A(H1N1) variants in the lower respiratory tract of critically ill patients during the 2010-2011 seasonal epidemic.

Piralla Antonio A Pariani Elena E Rovida Francesca F Campanini Giulia G Muzzi Alba A Emmi Vincenzo V Iotti Giorgio A GA Pesenti Antonio A Conaldi Pier Giulio PG Zanetti Alessandro A Baldanti Fausto F

PloS one 20111214 12

<h4>Background</h4>Since its appearance in 2009, the pandemic influenza A(H1N1) virus circulated worldwide causing several severe infections.<h4>Methods</h4>Respiratory samples from patients with 2009 influenza A(H1N1) and acute respiratory distress attending 24 intensive care units (ICUs) as well as from patients with lower respiratory tract infections not requiring ICU admission and community upper respiratory tract infections in the Lombardy region (10 million inhabitants) of Italy during the ...[more]

PMID: 22194826

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Project description:BackgroundOne dose of pandemic influenza vaccine Pandemrix (GlaxoSmithKline) was offered to the entire population of Finland in 2009-10. We conducted a prospective clinical cohort study to determine the vaccine effectiveness in preventing febrile laboratory-confirmed influenza infection during the influenza season 2009-10 and continued the study in 2010-11.MethodsIn total, 3,518 community dwelling adults aged 18-75 years living in Tampere city were enrolled. The participants were not assigned to any vaccination regimen, but they could participate in the study regardless of their vaccination status or intention to be vaccinated with the pandemic or seasonal influenza vaccine. They were asked to report if they received Pandemrix in 2009-10 and/or trivalent influenza vaccine in 2010-11. Vaccinations were verified from medical records. The participants were instructed to report all acute symptoms of respiratory tract infection with fever (at least 38°C) and pneumonias to the study staff. Nasal and oral swabs were obtained within 5-7 days after symptom onset and influenza-specific RNA was identified by reverse transcription polymerase chain reaction.ResultsIn 2009-10, the estimated vaccine effectiveness was 81% (95%CI 30-97). However, the vaccine effectiveness could not be estimated reliably, because only persons in prioritized groups were vaccinated before/during the first pandemic wave and many participants were enrolled when they already had the symptoms of A(H1N1)pdm09 influenza infection. In 2010-11, 2,276 participants continued the follow-up. The vaccine effectiveness, adjusted for potential confounding factors was 81% (95%CI 41-96) for Pandemrix only and 88% (95%CI 63-97) for either Pandemrix or trivalent influenza vaccine 2010-11 or both, respectively.ConclusionVaccination with an AS03-adjuvanted pandemic vaccine in 2009-10 was still effective in preventing A(H1N1)pdm09 influenza during the following epidemic season in 2010-11.Trial registrationClinicalTrials.gov NCT01024725. NCT01206114.

Dataset Information

Segregation of virulent influenza A(H1N1) variants in the lower respiratory tract of critically ill patients during the 2010-2011 seasonal epidemic.

Publications

Segregation of virulent influenza A(H1N1) variants in the lower respiratory tract of critically ill patients during the 2010-2011 seasonal epidemic.

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