Abstract
Following human infections with novel avian influenza A(H7N9) viruses in China, the European Centre for Disease Prevention and Control, the World Health Organization (WHO) Regional Office for Europe and the European Reference Laboratory Network for Human Influenza (ERLI-Net) rapidly posted relevant information, including real-time RT-PCR protocols. An influenza RNA sequence-based computational assessment of detection capabilities for this virus was conducted in 32 national influenza reference laboratories in 29 countries, mostly WHO National Influenza Centres participating in the WHO Global Influenza Surveillance and Response System (GISRS). Twenty-seven countries considered their generic influenza A virus detection assay to be appropriate for the novel A(H7N9) viruses. Twenty-two countries reported having containment facilities suitable for its isolation and propagation. Laboratories in 27 countries had applied specific H7 real-time RT-PCR assays and 20 countries had N9 assays in place. Positive control virus RNA was provided by the WHO Collaborating Centre in London to 34 laboratories in 22 countries to allow evaluation of their assays. Performance of the generic influenza A virus detection and H7 and N9 subtyping assays was good in 24 laboratories in 19 countries. The survey showed that ERLI-Net laboratories had rapidly developed and verified good capability to detect the novel A(H7N9) influenza viruses.
Highlights
On 31 March 2013, Chinese authorities announced the identification of a novel reassortant A(H7N9) influenza virus isolated from three unlinked fatal cases of severe respiratory disease in eastern China
A single preparation of viral RNA was made from a virus stock that had been passaged once more in eggs (E2/E1) and grown to an HA titre of 256/512 as assessed with turkey red blood cells. This virus stock yielded a concentration of 2x109 plaque forming units (PFU)/mL on Madin-Darby canine kidney (MDCK) cells. vRNA was extracted with a QIAamp vRNA extraction kit (Qiagen, catalogue no. #52906), and each influenza reference laboratory was supplied with 40 μL of an undiluted vRNA standard via dry-ice shipment
It was calculated that 5 μL of a 10−8 dilution of the vRNA standard would contain between 2.4 and 24 vRNA copies, assuming that 1 PFU equates to 10–100 virus particles
Summary
On 31 March 2013, Chinese authorities announced the identification of a novel reassortant A(H7N9) influenza virus isolated from three unlinked fatal cases of severe respiratory disease in eastern China. The Chinese Center for Disease Control and Prevention (CCDC) subtyped and sequenced the novel viruses and showed them to be low-pathogenic viruses of avian origin [2] This is the first time that human infection with avian influenza A(H7N9) virus and human deaths due to a low-pathogenicity avian influenza virus have been identified [3]. Detailed genetic sequence data from human, avian and environmental specimens and isolates of the novel avian influenza A(H7N9) viruses have been made available through the Global Initiative on Sharing All Influenza Data (GISAID) EpiFlu database and the International Nucleotide Sequence Database Collaboration (INSDC) These data suggest that multiple reassortment events have taken place, potentially involving wild birds [2,5,6,7].
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