The emergence of pandemic influenza A virus (pH1N1) in the spring of 2009 changed the way many microbiology laboratories detect not only influenza virus but also other respiratory viruses causing respiratory infections. Public health laboratories across Canada played a significant role in responding and providing services not only to detect this new virus, but also in maintaining other services essential for patient/outbreak management. This review addresses the approaches to pH1N1 laboratory testing across Canada and a subset of countries with similar health care systems, and strengths and weaknesses of these approaches.
Prior to the 2009 influenza pandemic, influenza was diagnosed in many laboratories by enzyme-linked immunosorbent assay (ELISA) or immunochromatographic tests (rapid influenza diagnostic tests; RIDT), immunofluorescence microscopy (direct fluorescent antibody tests; DFA), and/or shell vial or traditional virus culture. Some laboratories used nucleic acid amplification methods such as reverse-transcriptase- polymerase chain reaction (RT-PCR).
With the emergence of pandemic influenza A/H1N1 (pH1N1), nucleic acid tests became the principle method for the detection of respiratory viruses. By April 28, 2009 the National Microbiology Laboratory had provided primers and a protocol capable of identifying this novel strain, and most public health laboratories (PHLs) across the country, as well as many academic hospital microbiology laboratories, quickly verified and implemented a RT-PCR method for the detection of pH1N1 based on amplification of the matrix (M) and hemagglutination (HA) genes.
In addition to RT-PCR, multiplex assays were also used in some Canadian jurisdictions during the 2009 pandemic for detection of other circulating respiratory viral pathogens.
In anticipation of more intense testing activities during the second pandemic wave, the Pandemic Influenza Laboratory Preparedness Network (PILPN) issued guidelines for laboratory testing for the detection of pH1N1. Based on these guidelines and testing capacity, the majority of provinces prioritized testing based on risk groups, with highest priority given to patients who were hospitalized or part of an outbreak investigation.
To cope with the surge in influenza testing, personnel from other PHL departments were cross-trained to perform influenza tests. In addition, some PHLs suspended tests for other infectious agents, including norovirus PCR, viral culture on genital specimens, serology, respiratory viral and Mycoplasma pneumoniae culture, ova and parasite testing, bacterial typing, and HIV genotyping.
The emergence of pH1N1 in the spring of 2009 changed the way many microbiology laboratories detect not only influenza virus but also other respiratory viruses causing respiratory infections.