The Role of Punctuated Evolution in the Pathogenicity of Influenza Viruses
- Author: Jonathan A. McCullers1
- Editors: W. Michael Scheld2, James M. Hughes3, Richard J. Whitley4
-
VIEW AFFILIATIONS HIDE AFFILIATIONSAffiliations: 1: Department of Pediatrics, The University of Tennessee Health Sciences Center, Memphis, TN 38103; 2: Department of Infectious Diseases, University of Virginia Health System, Charlottesville, VA; 3: Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA; 4: Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL
-
Received 07 July 2015 Accepted 11 August 2015 Published 25 March 2016
- Correspondence: Jonathan A. McCullers, [email protected]

-
Abstract:
Influenza is an acute respiratory disease caused by influenza viruses. Evolutionarily, all influenza viruses are zoonoses, arising in the animal reservoir and spilling over into the human population. Several times a century, one of these zoonotic events results in a new influenza virus lineage becoming established in humans and circulating for years or decades as an endemic strain. The worldwide pandemic that occurs shortly after the nascent virus becomes established can have a profound impact on morbidity and mortality. Because influenza viruses continually evolve and the illness they engender can vary considerably based on characteristics of the strain, the weather, other circulating or endemic pathogens, as well as the number of susceptible hosts, the impact of each season on human health is unpredictable. Over time, the general pattern is for pandemic strains to adapt and gradually take on characteristics of seasonal strains with lower virulence and a diminished synergism with bacterial pathogens. Study of this punctuated evolution yields a number of insights into the overall pathogenicity of influenza viruses.
-
Citation: McCullers J. 2016. The Role of Punctuated Evolution in the Pathogenicity of Influenza Viruses. Microbiol Spectrum 4(2):EI10-0001-2015. doi:10.1128/microbiolspec.EI10-0001-2015.




The Role of Punctuated Evolution in the Pathogenicity of Influenza Viruses, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/microbiolspec/4/2/EI10-0001-2015-1.gif /docserver/preview/fulltext/microbiolspec/4/2/EI10-0001-2015-2.gif

References

Article metrics loading...
Abstract:
Influenza is an acute respiratory disease caused by influenza viruses. Evolutionarily, all influenza viruses are zoonoses, arising in the animal reservoir and spilling over into the human population. Several times a century, one of these zoonotic events results in a new influenza virus lineage becoming established in humans and circulating for years or decades as an endemic strain. The worldwide pandemic that occurs shortly after the nascent virus becomes established can have a profound impact on morbidity and mortality. Because influenza viruses continually evolve and the illness they engender can vary considerably based on characteristics of the strain, the weather, other circulating or endemic pathogens, as well as the number of susceptible hosts, the impact of each season on human health is unpredictable. Over time, the general pattern is for pandemic strains to adapt and gradually take on characteristics of seasonal strains with lower virulence and a diminished synergism with bacterial pathogens. Study of this punctuated evolution yields a number of insights into the overall pathogenicity of influenza viruses.

Full text loading...
Figures
Influenza A virus life cycle in cells.

Click to view
FIGURE 1
Influenza A virus life cycle in cells.
Influenza A virus ecology. The wild-bird reservoir is the source of all zoonotic influenza A viruses. These viruses cross over into humans through intermediate species, such as domestic poultry and swine. Farm animal silhouettes by Otutor, used under License CC BY 3.0 (https://creativecommons.org/licenses/by/3.0/us/); oyster catcher silhouette courtesy of Rachison Alexandra; human silhouettes courtesy of Mackey Creations.

Click to view
FIGURE 2
Influenza A virus ecology. The wild-bird reservoir is the source of all zoonotic influenza A viruses. These viruses cross over into humans through intermediate species, such as domestic poultry and swine. Farm animal silhouettes by Otutor, used under License CC BY 3.0 (https://creativecommons.org/licenses/by/3.0/us/); oyster catcher silhouette courtesy of Rachison Alexandra; human silhouettes courtesy of Mackey Creations.
Pandemic timeline. Four major lineages of influenza A virus have established endemicity in humans in the last century. The 1957 and 1968 pandemic viruses were reassortants which included genes from the previously circulating viruses which they replaced. The 1918 and 2009 pandemic strains came directly from animal reservoirs. The seasonal H1N1 lineage which circulated early in the 20th century was replaced in 1957 but reemerged in 1976 and cocirculated for 32 years with seasonal H3N2 strains.

Click to view
FIGURE 3
Pandemic timeline. Four major lineages of influenza A virus have established endemicity in humans in the last century. The 1957 and 1968 pandemic viruses were reassortants which included genes from the previously circulating viruses which they replaced. The 1918 and 2009 pandemic strains came directly from animal reservoirs. The seasonal H1N1 lineage which circulated early in the 20th century was replaced in 1957 but reemerged in 1976 and cocirculated for 32 years with seasonal H3N2 strains.
Tables
Influenza A virus gene functions

Click to view
TABLE 1
Influenza A virus gene functions
Supplemental Material
No supplementary material available for this content.