An article by Steven Sternberg and colleagues is set to appear in the May issue of the journal Emerging Infectious Diseases. In it, the authors describe the results of complete genome sequence comparisons for 36 recent isolates of the avian flu virus (influenza H5N1). Their results “clearly depict the lineages now infecting wild and domestic birds in Europe and Africa and show the relationships among these isolates and other strains affecting both birds and humans”. More specifically,
The isolates fall into 3 distinct lineages, 1 of which contains all known non-Asian isolates. This new Euro-African lineage, which was the cause of several recent (2006) fatal human infections in Egypt and Iraq, has been introduced at least 3 times into the European-African region and has split into 3 distinct, independently evolving sublineages.
Figure 1. Phylogenetic tree of hemagglutinin (HA) segments from 36 avian influenza samples. A 2001 strain (A/duck/Anyang/AVL-1/2001) is used as an outgroup at top. Clade V1 comprises the 5 Vietnamese isolates at the bottom of the tree, and clade V2 comprises the 9 Vietnamese isolates near the top of the tree. The European-Middle Eastern-African (EMA) clade contains the remaining 22 isolates sequenced in this study; the 3 subclades are indicated by red, blue, and purple lines. The reassortant strain, A/chicken/Nigeria/1047–62/2006, is highlighted in red.
This is a study in phylogenetics — that is, it reconstructs evolutionary relationships among viral strains using the same tools that many evolutionary biologists use to study the relationships among species. It is well known that viruses evolve very rapidly, and tracking their their past changes contributes to the ability to predict future ones. As the authors conclude,
These findings show how whole-genome analysis of influenza (H5N1) viruses is instrumental to the better understanding of the evolution and epidemiology of this infection, which is now present in the 3 continents that contain most of the world’s population. This and related analyses, facilitated by global initiatives on sharing influenza data, will help us understand the dynamics of infection between wild and domesticated bird populations, which in turn should promote the development of control and prevention strategies.
Evolution is not something that only happened to the myriad fossil specimens housed in museum drawers, and evolutionary biology is not merely relevant to academics tucked away in research labs. Evolution is both an ongoing process and an active and exciting area of research. More than ever, an understanding of the processes involved is relevant to the well-being of people from all regions of the world.