New perspective article from NEJM: "The Persistant Legacy of the 1918 Influenza Virus"P

NEJM just published a great perspectives article on recent findings/thinking about the 1918 virus with an easy to understand analogy of the gene segments of the virus:

"To understand what has been happening since 1918, it is helpful to think of influenza viruses not as distinct entities but as eight-member "gene teams" that work together and must sometimes trade away one or more team members to make way for new gene "players" with unique skills. In nature, avian influenza A viruses seem to exist as transient complexes of eight genes that assemble and reassemble promiscuously, if not randomly, in an enormous global avian reservoir. Within this reservoir, avian viruses remain stably adapted to the enteric tracts of hundreds of avian species, single members of which are often simultaneously infected by multiple viruses that engage in prolific gene reassortment. Because of this continual reassortment, a seemingly endless variety of new viruses with potentially new properties are continually being engineered. Indeed, thousands of unique gene constellations making up avian influenza viruses have already been identified; as research continues, the number will undoubtedly grow."


Most interesting to me was this article seems to continue some of the thinking from this weeks PNAS article in challenging some previously held notions,

"But the long-held belief that shifts always cause severe pandemics, whereas drifts lead to more modest increases in seasonal mortality, has been called into question. The effects on mortality of new influenza viruses created by the several genetic mechanisms mentioned above are not easily characterized"

Conclusion was interesting as well:

"If there is good news, it is that successive pandemics and pandemic-like events generally appear to be decreasing in severity over time. This diminution is surely due in part to advances in medicine and public health, but it may also reflect viral evolutionary "choices" that favor optimal transmissibility with minimal pathogenicity — a virus that kills its hosts or sends them to bed is not optimally transmissible. Although we must be prepared to deal with the possibility of a new and clinically severe influenza pandemic caused by an entirely new virus, we must also understand in greater depth, and continue to explore, the determinants and dynamics of the pandemic era in which we live."

Highly recommend the quick read: http://content.nejm.org/cgi/content/full/361/3/225