Influenza A/H1N1/2009 virus - experience of the clinical microbiology laboratory of the “L. Sacco” University Hospital in Milan

  • Lisa Lucia Chenal |
  • Alessandra Lombardi
  • Nadia Zanchetta
  • Giuseppe Giuliani
  • Valeria Micheli
  • Sara Giordana Rimoldi
  • Loredana Tocalli
  • Cristina Pagani
  • Maria Rita Gismondo


In the spring of 2009, a new variant of influenza A/H1N1 virus that had never been isolated before, was identified. From April 27 to December 31, 2009 the respiratory samples of 974 patients, obtained from suspected cases of pandemic influenza A virus infection, were analyzed at the Clinical Microbiology Laboratory of the “L. Sacco” University Hospital in Milan. The diagnosis of influenza A/H1N1 infection was performed initially through the use of different molecular biological methods: Seeplex® RV12 ACE Detection (Seegene), NUCLISENS® EASYQ® INFLUENZA A/B (bioMérieux), Influenza A/B Q-PCR Alert (Nanogen) running in parallel with rRT-PCR (CDC) to confirm the positivity to the new influenza virus, then was used a single specific test, Fast set H1N1v (Arrow Diagnostics). Retrospective study of data showed that 293 (30.1%) patients were positive for the new strain of influenza A/H1N1 virus and 8 (0.8%) for influenza A other than H1N1 virus.The distribution of influenza A/H1N1 cases showed two peaks, one on July (62.9%) and the other one on October (36%), moreover we observed that 155 patients (53%) out of 293 positive for influenza A/H1N1 virus aged under 20 years old. The first positivity peak was found in travelers and the second one, occurred 2-3 months prior to the classic seasonal epidemic influenza, was attributed to autochthonous cases , by which the virus had spread worldwide. The highest proportion of cases were among subjects aged from 0 to 20 years and, over this age the positivity rate decreased proportionally with increasing age, in agreement with data reported in other countries.



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Original Articles
Influenza A/H1N1 2009 virus, Reverse Transcription Polymerase Chain Reaction (RT-PCR)
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How to Cite
Chenal, L. L., Lombardi, A., Zanchetta, N., Giuliani, G., Micheli, V., Rimoldi, S. G., Tocalli, L., Pagani, C., & Gismondo, M. R. (2011). Influenza A/H1N1/2009 virus - experience of the clinical microbiology laboratory of the “L. Sacco” University Hospital in Milan. Microbiologia Medica, 26(2).

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