Children and young adults have been most affected, both in terms of numbers of cases and severity of disease.
Perhaps the most striking feature of the pandemic so far is that fewer than half of those hospitalized or killed by this virus have had identifiable prior medical conditions or risk factors.
Most existing swine data were derived from opportunistic samples collected from diseased pigs in disparate geographical regions, not from prospective studies in defined locations, hence the evolutionary and transmission dynamics of Sw IV are poorly understood.
Here we quantify the epidemiological, genetic and antigenic dynamics of Sw IV in Hong Kong using a data set of more than 650 Sw IV isolates and more than 800 swine sera from 12years.
Furthermore, the unsampled history of the epidemic means that the nature and location of the genetically closest swine viruses reveal little about the immediate origin of the epidemic, despite the fact that we included a panel of closely related and previously unpublished swine influenza isolates.
Our results highlight the need for systematic surveillance of influenza in swine, and provide evidence that the mixing of new genetic elements in swine can result in the emergence of viruses with pandemic potential in humans Initial genetic characterization of the S-OIV outbreak by the United States Centers for Disease Control suggested swine as its probable source, on the basis of sequence similarity to previously reported swine influenza isolates.
Intercontinental virus movement has led to reassortment and lineage replacement, creating an antigenically and genetically diverse virus population whose dynamics are quantitatively different from those previously observed for human influenza viruses.
Here we use evolutionary analysis to estimate the timescale of the origins and the early development of the S-OIV epidemic.
A novel H1N1 influenza virus has emerged from an animal reservoir and is spreading globally. Update: infections with a swine-origin influenza A (H1N1) virus—United States and other countries, April 28, 2009.
Surprisingly, however, much of the severe disease that is occurring with this new pandemic strain is also manifesting in school-age children and young adults, groups that are typically spared the most serious outcomes during seasonal influenza.
The new avianlike H1N1 swine viruses in Europe may provide a model for the evolution of newly introduced avian viruses into the swine host reservoir.
The NPs of these viruses are evolving more rapidly than those of human or classical swine viruses (4.50 nucleotide changes and 0.74 amino acid change per year), and when these rates are applied to pre-1930s human and classical swine virus NPs, the predicted date of a common ancestor is 1918 rather than 1912 to 1913.