Preparing the outbreak assistance laboratory network in the Netherlands for the detection of the influenza virus A(H1N1) variant

Background: Late April 2009, human infection with variant influenza virus A(H1N1)v emerged in the Northern Americas posing a threat that this virus may become the next pandemic influenza virus. Objectives: To prepare laboratories for surge capacity for molecular diagnosis of patients suspected for A(H1N1)v infection in the Netherlands. Study design: A panel of 10 blinded specimens containing seasonal A(H1N1) or A(H3N2), or A/Netherlands/602/2009(H1N1)v influenza virus, or negative control was distributed to the outbreak assistance laboratories (OAL) together with influenza virus A (M-gene), swine influenza virus A (NP-gene) and influenza virus A(H1N1)v (H1v-gene) specific primers and probes and protocol (CDC Atlanta, USA). Laboratories were asked to implement and test this protocol. Results: All OAL were able to detect A(H1N1)v using the CDC M-gene reagents, the majority with similar sensitivity as the in-house M-gene based assays. RT-PCRs used in routine diagnostic setting in the OAL specifically designed to detect H1, H3, or NS1 from seasonal influenza A viruses, did not or at very low level cross-react with A(H1N1)v. The CDC swine NP-gene and H1v-gene RT-PCRs showed somewhat reduced sensitivity compared to the CDC and in-house M-gene RT-PCRs. In contrast, in-house developed A(H1N1)v specific H1v-gene and N1v-gene RT-PCRs showed equal sensitivity to CDC and in-house M-gene RT-PCRs. Conclusions: The Dutch OAL are prepared for detection and specific identification of A(H1N1)v, although some level of cross-reactivity was observed with seasonal influenza viruses. Additionally, M-gene based generic influenza A virus detection is recommended to be able to detect emerging influenza A viruses in routine settings.

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