Evolution

2 Men in China Die of Lesser-Known Strain of Bird Flu

https://www.osc.edu/press/researchers-take-virus-tracking-software-worldwide
Link ~ ~ Megan J Rutherford ~ 6 Comments

2 Men in China Die of Lesser-Known Strain of Bird Flu

The H7N9 Strain of Avian Influenza Virus (AIV) is Rare but Deadly

The three reported cases of H7N9 AIV are not linked and no other close contacts, such as family members have shown any symptoms as of March 31, 2013 but doctors are carefully monitoring the family.  Currently there does not appear to be any threat to the community.

Clinical Presentation of H7N9 and Treatment

All three cases of documented H7N9 began with fever, cough, respiratory tract infection, and pneumonia during the early stages of the illness. Five to ten days after the illness beganvere pneumonia with difficulty breathing, and some progressed into respiratory distress and two of the three died.

Treatment for H7N9 is limited to anti-influenza virus drugs; however, further research is needed to determine if this is the most effective treatment option.

The Avian Influenza Virus Becomes a Powerful Pathogen When Crossing the Species Barrier

Influenza A virus originates in ducks and expresses relatively mild symptoms in its ecological niche.  However, when the virus mutates and crosses species barriers it becomes a powerful pathogen.  Other bird species and mammals are more severely affected with symptoms ranging from very mild to very severe and ultimately death.  Figure 1 below shows how the virus can cross species barriers and mutate into different pathogenic strains.

Figure 1 - Influenza A Virus - Dabbling Duck - Illustration of the host range of influenza A virus with the natural reservoir of influenza A virus, accidental hosts, and the subtypes that have been identified in the different groups. Illustration by Rebecca Rönnmark and Eric Gisaeus.
Figure 1 – Influenza A Virus – Dabbling Duck – Illustration of the host range of influenza A virus with the natural reservoir of influenza A virus, accidental hosts, and the subtypes that have been identified in the different groups. Illustration by Rebecca Rönnmark and Eric Gisaeus.

Bioinformatics Provides Us With Tools to Trace The Avian Influenza Family Tree (Phylogenetics)

Phylogenetic analysis can be used to trace viral infection through a human population, and the Comparative Method uses phylogenies to trace the evolution of a specific genetic sequence or trait across different species.  Phylogentics is defined as the study of evolutionary relatedness among various groups of organisms through molecular sequencing data and morphological data matrices. Sequencing of DNA, RNA, and proteins provides us with genomic information that can be stored and used in computer analysis programs.  These programs employ algorithms to predict mutations and construct cladistics or phylogenetic (evolutionary) trees.

http://www.pnas.org/content/102/51/18590/F3.expansion.html
Figure 2 – Example of Phylogenetic Analysis of the viral polymerase that mediates adaptation of an avian influenza virus to a mammalian host

Copyright © 2005, The National Academy of Sciences

Cladistics and the Spread of the Avian Influenza

Cladistics refers to the scientific classification of living organisms, based on common ancestry, into evolutionary trees. Evolutionary trees are used by many researchers studying infectious diseases to understand the geographic and host origins of pathogens and how the pathogens change over time. Supramap puts phylogenies in a geographic context as well.

https://www.osc.edu/press/researchers-take-virus-tracking-software-worldwide
Figure 3 – Cladistics – AIV (H7) in 2012 – Screenshot of the spread of H7 influenza as produced by SUPRAMAP and visualized by Google Earth™. This view illustrates the historical spread of high pathogenic lineages (high-altitude red lines) and the recent local evolution of high pathogenicity (low-altitude red lines). [credit: Janies/OSU]
Resources:

Chinese Center for Disease Control and Prevention. Questions and answers about human infection with H7N9 avian influenza. (2013). Accessed April 1, 2013.

Decoded Science. Bird Flu H7N9: First Human Deaths in China. (2013). Accessed April 1, 2013

Infection Ecology and Epidemiology 2011. © 2011 John Wahlgren. This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial 3.0 Unported License (http://creativecommons.org/licenses/by-nc/3.0/), permitting all non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Ohio Super Computer Center. Researchers take virus tracking software worldwide. (2012). Accessed April 1, 2013

New York Times. 2 Men in China die of lesser-known strain of bird flu. (2013). Accessed April 1, 2013.

Gabriel G, Dauber B, Wolf T; et al. (2005) The viral polymerase that mediates adaptation of an avian influenza virus to a mammalian host. Proceedings of the National Academy of Sciences of the United States of America 102 (51 18590-18595) doi:10.1073/pnas.0507415102

World Health Organization. Avian Influenza Fact Sheet. (2011). Accessed April 1, 2013.