Influenza

Abstract

Influenza is an infectious respiratory disease that, in humans, is caused by influenza A and influenza B viruses. Typically characterized by annual seasonal epidemics, sporadic pandemic outbreaks involve influenza A virus strains of zoonotic origin. The WHO estimates that annual epidemics of influenza result in ~1 billion infections, 3–5 million cases of severe illness and 300,000–500,000 deaths. The severity of pandemic influenza depends on multiple factors, including the virulence of the pandemic virus strain and the level of pre-existing immunity. The most severe influenza pandemic, in 1918, resulted in >40 million deaths worldwide. Influenza vaccines are formulated every year to match the circulating strains, as they evolve antigenically owing to antigenic drift. Nevertheless, vaccine efficacy is not optimal and is dramatically low in the case of an antigenic mismatch between the vaccine and the circulating virus strain. Antiviral agents that target the influenza virus enzyme neuraminidase have been developed for prophylaxis and therapy. However, the use of these antivirals is still limited. Emerging approaches to combat influenza include the development of universal influenza virus vaccines that provide protection against antigenically distant influenza viruses, but these vaccines need to be tested in clinical trials to ascertain their effectiveness.Influenza is an infectious respiratory disease that, in humans, is caused by influenza A and influenza B viruses. This Primer discusses the biological features of influenza viruses, their effects on human and animal health and the mitigation strategies to reduce the burden of this disease.

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Affiliated Institutions

• Duke-NUS Medical School SG
• University of Rochester US
• The University of Melbourne AU
• Peter Doherty Institute AU
• St. Jude Children's Research Hospital US
• Icahn School of Medicine at Mount Sinai US
• Erasmus MC NL
• University of Hong Kong HK
• Erasmus University Rotterdam NL

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