2009 H1N1 influenza

Abstract

Within 2 months of its discovery last spring, a novel influenza A (H1N1) virus, currently referred to as 2009 H1N1, caused the first influenza pandemic in decades. The virus has caused disproportionate disease among young people with early reports of virulence similar to that of seasonal influenza. This clinical review provides an update encompassing the virology, epidemiology, clinical manifestations, diagnosis, treatment, and prevention of the 2009 H1N1 virus. Because information about this virus, its prevention, and treatment are rapidly evolving, readers are advised to seek additional information. We performed a literature search of PubMed using the following keywords: H1N1, influenza, vaccine, pregnancy, children, treatment, epidemiology, and review. Studies were selected for inclusion in this review on the basis of their relevance. Recent studies and articles were preferred.

FIGURE 1.

Structural diagram of the H1N1 virus. H = hemagglutinin; M = matrix; N = neuraminidase; NP = nucleoprotein; NS = nonstructural; PA = acidic polymerase; PB = basic polymerase From Science, with permission.

FIGURE 2.

Origins of each of the 8 genomic segments of the 2009 H1N1 virus (designated H1N1 S-OIV 2009 in this figure). Host species are represented by colored boxes: avian (green), swine (red), and human (grey). Interspecies-transmission pathways of influenza genes are represented by colored lines. Note that the N1 and M genomic segments (in yellow) are derived from an H1N1 Eurasian swine virus that is a genomic descendent of the infamous H1N1 avian virus that crossed the species barrier to cause the 1918 influenza pandemic. The remaining 6 genomic segments are derived from the triple-reassortant swine-origin influenza virus that contains genomic material from the classic H1N1 swine influenza virus, the seasonal H3N2 virus, and the H1N1 avian virus. H = hemagglutinin; M = matrix; N = neuraminidase; NP = nucleoprotein; NS = nonstructural; PA = acidic polymerase; PB = basic polymerase. Reprinted with permission from Macmillan Publishers, Ltd: Nature (http://www.nature.com). Copyright © 2009.