Avian influenza A(H7N9) virus infection

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Described in majority of patients in case series.

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Described in majority of patients in case series.

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A chest x-ray alone cannot exclude or differentiate viral or bacterial pneumonia.

Lung infiltrates are commonly bilateral, diffuse (lower, middle, and upper zones can be affected), and show both central and peripheral distribution.[122]Feng F, Jiang Y, Yuan M, et al. Association of radiologic findings with mortality in patients with avian influenza H7N9 pneumonia. PLoS One. 2014 Apr 4;9(4):e93885. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0093885 http://www.ncbi.nlm.nih.gov/pubmed/24705783?tool=bestpractice.com

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Indicated in patients with dyspnea or suspected pneumonia.

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Primary bacterial pneumonia and potential bacterial coinfection should be evaluated. Coinfections have been reported in Asian lineage A(H7N9) virus-infected patients, but mainly hospital-acquired bacterial infections and ventilator-associated pneumonia.

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Primary bacterial pneumonia and potential bacterial coinfection should be evaluated in severely ill patients.

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Recommended for diagnosis of Asian lineage A(H7N9) virus infection. Should be performed in patients with signs or symptoms consistent with influenza-like illness or acute respiratory tract infection who have a relevant epidemiologic history.[111]Centers for Disease Control and Prevention. Interim guidance on testing and specimen collection for patients with suspected infection with novel influenza A viruses with the potential to cause severe disease in humans. Jun 2023 [internet publication]​. https://www.cdc.gov/flu/avianflu/severe-potential.htm ​​[115]World Health Organization. Real-time RT-PCR protocol for the detection of avian influenza A(H7N9) virus. Apr 2013 [internet publication]. https://www.who.int/publications/m/item/real-time-rt-pcr-protocol-for-the-detection-of-avian-influenza-a(h7n9)-virus [116]Torres A, Lee N, Cilloniz C, et al. Laboratory diagnosis of pneumonia in the molecular age. Eur Respir J. 2016 Dec;48(6):1764-78. https://erj.ersjournals.com/content/48/6/1764.long http://www.ncbi.nlm.nih.gov/pubmed/27811073?tool=bestpractice.com [117]World Health Organization. WHO information for the molecular detection of influenza viruses. Feb 2021 [internet publication]. https://www.who.int/teams/global-influenza-programme/laboratory-network/quality-assurance/eqa-project/information-for-molecular-diagnosis-of-influenza-virus [118]Centers for Disease Control and Prevention. Diagnostics for detecting H7N9 using rRT-PCR. May 2022 [internet publication]. https://www.cdc.gov/flu/avianflu/h7n9/detecting-diagnostics.htm

Infection prevention and control precautions are recommended when collecting specimens. Preferred specimens in nonintubated patients are upper respiratory tract specimens (e.g., oropharyngeal swab, nasopharyngeal swab, nasal aspirate or wash). Preferred specimens in intubated patients or patients with severe lower respiratory tract illness are lower respiratory tract specimens (e.g., endotracheal aspirate, bronchoalveolar lavage fluid). Multiple respiratory specimens should be collected from different sites on at least two consecutive days for hospitalized patients. Swabs with a synthetic tip (e.g., Dacron®, polyester) or an aluminum or plastic shaft should be used. Obtain specimens as soon as possible, ideally within 7 days of symptom onset.[111]Centers for Disease Control and Prevention. Interim guidance on testing and specimen collection for patients with suspected infection with novel influenza A viruses with the potential to cause severe disease in humans. Jun 2023 [internet publication]​. https://www.cdc.gov/flu/avianflu/severe-potential.htm ​​

RT-PCR for A(H7N9) viruses is usually not available in many clinical settings, where detection of nonsubtyped influenza A virus is more typical. Many regional public health laboratories, most national laboratories, and some private laboratories can perform RT-PCR for A(H7N9) virus, or RT-PCR for avian A(H7) viruses with subsequent virus characterization by genetic sequencing. If subtyping of a detected influenza A virus has been attempted locally, but seasonal A(H1) and A(H3) viruses could not be detected ("unsubtypable influenza A"), the sample should be referred to a reference laboratory for further characterization.

May take several hours to produce preliminary results, but transport time and testing logistics may delay testing results.

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Virus culture will not produce timely results for clinical management and must be performed in a biosafety level 3-enhanced (BSL 3+) laboratory. Viral culture can be performed at World Health Organization (WHO) avian influenza reference laboratories and WHO collaborating influenza centers.

Viral culture is important for virologic surveillance, antigenic monitoring for vaccine strain selection, and assessment and analyses of viral characteristics such as genetic reassortment, receptor binding affinity, and antiviral susceptibility.

Clinical specimens testing positive for A(H7N9) virus RNA by reverse transcription polymerase chain reaction may be cultured by a WHO avian influenza reference laboratory or WHO collaborating influenza center laboratory.