Influenza virus types A and -B

Useful For


Rapid and accurate detection of influenza A and influenza B virus infection


Clinical Information


Common symptoms of influenza infection include fever, chills, sore throat, muscle pains, severe headache, weakness/fatigue, and a nonproductive cough. Certain patients, including infants, the elderly, the immunocompromised, and those with impaired lung function, are at risk for serious complications. Influenza viruses cause annual outbreaks of influenza worldwide. In Canada, influenza or “flu” season usually runs from November to April and an estimated 10-25% of Canadians may get the flu each year. Although most of these people recover completely, an estimated 4,000 to 8,000 Canadians, mostly seniors, die every year from pneumonia related to influenza and many others may die from other serious complications of influenza.


Influenza infection may be treated with supportive therapy, as well as antiviral drugs such as the neuraminidase inhibitors, oseltamivir (TAMIFLU) and zanamivir (RELENZA), and the adamantanes, rimantadine and amantadine. These drugs are most effective when given within the first 48 hours of infection, so prompt diagnosis and treatment are essential for proper management.


Influenza viruses belong to the family Orthomyxoviridae and are enveloped viruses that may exist in spherical or filamentous forms of 80 to 120 nm, with surface projections that consist of HA and NA spikes. Influenza, otherwise known as the “flu,” is an acute, contagious respiratory illness caused by influenza A, B, and C viruses. Of these, only influenza A and B are thought to cause significant disease, with infections due to influenza B usually being milder than infections with influenza A. Influenza A viruses are further categorized into subtypes based on the 2 major surface protein antigens: hemagglutinin (H) and neuraminidase (N).




A positive result indicates that virus was present in the specimen submitted. Clinical correlation is necessary to determine the significance of this finding as asymptomatic, persistent, or recurrent adenovirus infections can occur.


Negative results may be seen in a number of situations including absence of viral disease, nonviable organisms submitted or suboptimal specimen collection/transport.


Clinical Reference


Atmar, R. L. 2007. Influenza Viruses, p. 1340-1351. In Murray, P. R., Baron, E. J., Jorgensen, J. H., Landry, M. L., and Pfaller, M. A. Manual of Clinical Microbiology, 9th ed., vol. 2. ASM Press, American Society for Microbiology, Washington, DC.


Treanor, J. J. 2010. Influenza Viruses, Including Avian Influenza and Swine Influenza, p. 2265-2288. In Mandell, D., Bennett, J. E., and Dolin, R. Principles and practice of infectious diseases, 7th ed., vol. 2. Churchill Livingstone, Elsevier, Philadelphia, PA.




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