Que sera, sera: evolution of the swine H1N1 influenza A virus

Abstract

A new human influenza A virus (IAV) strain of swine-like origin emerged in Mexico and the United States in March and April of 2009 [1]. The virus disseminated globally with sufficient celerity that on June 11, 2009 the World Health Organization (WHO) raised the Flu Pandemic Alert Level to Phase 6, officially designating a new global pandemic. At this time there were 30,000 confirmed cases in 74 countries. Less than a month later (as of July 1, 2009), the WHO confirmed over 77,000 cases with 332 deaths. The collaborative nature of the global response to the outbreak has been remarkable. Within days of the initial reporting of the virus, researchers completely sequenced the genome of several viral isolates and posted the sequences on the internet. Sequences of new isolates continue to be uploaded daily on websites such as the Global Initiative on Sharing Avian Influenza Data (http:platform.gisaid.org) and the National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/genomes/FLU/SwineFlu/html). Nearly in real time, phylogeneticists identified the complex origins of the virus. Within weeks, a vaccine seed stock was isolated, and the private and public sector began intense collaborative efforts to produce a vaccine post-haste [2]. This is the first major introduction of a pandemic influenza strain since 1977, and the first to benefit from the biotechnology revolution. Those looking to defend the investment of world governments into biomedical research have another shining example of the enormous payoff in both lives and money gained from achieving a better understanding of biology. Retrospectively, concerns over the pandemic potential of avian IAVs prepared society well for the current pandemic, as recently upgraded resources have played critical roles in monitoring and responding rapidly. Scientists, physicians, administrators, and politicians who fought for these resources deserve the gratitude of their nations. Clearly, appropriate actions have been taken to limit disease and death associated with the new virus. The contrast with the 1918 pandemic, whose causative agent was not known for 13 years, could not be starker. Despite our advances, it is critical to recognize that today, as in 1918, humanity can neither control nor predict the genetic and antigenic evolution of this virus. Here we discuss factors in the evolution of 2009 swine-origin H1N1 IAV (hereafter referred to as S-IAV-2009).