Pandemic (H1N1) 2009 virus revisited: An evolutionary retrospective

Abstract

The pandemic (H1N1) 2009 virus is unique in many aspects, especially in its genetics and evolution. In this paper, we examine the molecular mechanisms underlying the evolution of this novel virus through a comprehensive bioinformatics analysis, and present results in the context of a review of the literature. The pandemic virus was found to arise from a reassortment of two swine viruses, each of which ultimately arose from interspecies transmission. It experienced fast evolutionary rates and strong selection pressures, diverging into two different clusters at the early pandemic stage. Cluster I became extinct at the end of 2009 whereas cluster II continued to circulate at much lower rates in 2010. Therefore, on August 10 of 2010 the WHO declared the end of the pandemic. Important mutations associated with host specificity, virulence, and drug resistance were detected in the pandemic virus, indicating effective transmission and increased severity in humans. Much has been learned about the evolutionary dynamics of this pandemic virus; however, it is still impossible to predict when the next pandemic will occur and which virus will be responsible. Improved surveillance at different levels (both national and international) and in different hosts (especially in swine) appears to be crucial for early detection and prevention of future influenza pandemics.

Evolution trends of the 2009 pandemic influenza A (H1N1) viruses in different continents from March 2009 to April 2012

“…We delivered graphic representations of HA and NA sequences of different continents (Figs 3 and 4) so that it is possible to draw some conclusions. The viruses in (Fereidouni et al 2009;Nelson et al 2009;Shiino et al 2009;Christman et al 2011). Besides of the found clusters, the graphic representations (Figs 3a, 4a) show a new major cluster (x < −1 and y > 1.5 in Fig.…”

The E119D neuraminidase mutation identified in a multidrug-resistant influenza A(H1N1)pdm09 isolate severely alters viral fitness in vitro and in animal models

“…The difference in our results could also be related to the different viral backgrounds used in the two studies. Indeed, the A/California/04/ 2009 viral genome belongs to cluster I that appeared in early April 2009 and disappeared by the end of 2009 whereas the genome of A/Quebec/144147/09 strain belongs to cluster II that emerged later and has been circulating since (Christman et al, 2011). A few genetic differences obviously exist between the two strains as summarized in Table S2.…”

Review on Swine Flu and Status of Swine Flu in Ethiopia

“…In 2009, a novel H1N1 virus emerged in human populations. It causes respiratory and gastrointestinal symptoms in human with death related to other bacterial complications [41][42][43]. Infections with various H1N1, H3N2 and H1N2 swine influenza viruses are reported sporadically in humans.…”