Evolution and ecology of influenza a viruses request pdf. Here, we investigated the evolutionary, spatial and temporal dynamics of avian iavs in eurasian wild birds. Pandemic and seasonal influenza a virus ecology, epidemiology and evolution of infectious disease research group justin bahl justin. Longdistance transport of the virus is tied to inter. Origins, ecology and epidemiology of pandemic and seasonal.
Influenza viruses infect many vertebrates, with influenza a, b and c viruses iav, ibv, and icv infecting humans. Information the rapid evolution of influenza viruses. It is widely accepted that all influenza virus strains infecting mammalian species originate from wild birds 2, 3. Influenza a viruses also infect poultry, pigs, horses, dogs, and occasionally sea mammals. Genome sequencing, antigenic mapping and epidemiological modelling are enhancing our understanding of the evolution of human influenza virus. Its genetic information is segmented and consists of 8 separate singlestranded rnamolecules, which encode a total of 11 different viral proteins. The epidemiological study of aivs in ducks 20082011 revealed an overall virus detection rate of 7.
Although in a relatively stable host pathogen interaction in aquatic birds, antigenic, and genetic evolution of influenza a viruses often accompanies interspecies transmission as the virus adapts to a new host. The virus causing influenza is one of the best known pathogens found in various species. Influenza a virus iav has caused significant morbidity and mortality globally in humans, with an estimated 14 pandemics that have occurred since the 1500s. Adaptive evolution and environmental durability jointly.
A key concept in influenza virus evolution is that there is a marked difference in evolutionary dynamics between those viruses that infect aquatic birds and those from other host species. Influenza a virus belongs to the family orthomyxoviridae, a family of viruses with a. This new edition has been completely revised and reflects the integration of disciplines concerning the emergence, evolution, pathogenesis and control of influenza. Influenza virus replication depends on the biosynthetic machinery of the cell and is under the control of the defense mechanisms developed by the host against infec tion shaw and palese, 20. The phylogeny, or the evolutionary history of a particular species, is an important component when analyzing the evolution of influenza. The patterns and processes of influenza virus evolution are of fundamental importance, underpinning such traits as the propensity to emerge in. Influenza a viruses have been isolated from many animal species, but wild waterfowl and shorebirds are recognized as their natural reservoirs due to the prevalence of the highest diversity of influenza a virus among these hosts. Iav from different host species can reassort their segmented genomes, producing pandemic strains that are antigenically novel but otherwise well adapted to humans. Climate change and avian influenza university of oklahoma.
Prevalence, transmission and evolution of avian influenza. To complete their life cycle, influenza viruses have evolved. Wild birds of the orders anseriformes such as ducks and geese and charadriiformes such as shorebirds and gulls are the primary reservoir of avian influenza viruses. Low pathogenic avian influenza a viruses iavs have a natural host reservoir in wild waterbirds and the potential to spread to other host species. This is to ensure that we give you the best experience possible. Avian influenza h5n1 and the evolutionary and social ecology of. Influenza b viruses are pathogens of humans only, and although influenza c viruses infect humans and pigs, these viruses rarely cause serious disease. Further evidence that wild birds constitute a reservoir for influenza a virus comes from studies on viral evolution, which have shown limited. This paper will address that question firstly in relation to. Although in a relatively stable hostpathogen interaction in aquatic birds, antigenic, and genetic evolution of influenza a viruses often accompanies interspecies transmission as the virus adapts to a new host. The evolutionary dynamics of influenza a virus within and. Ecology and evolution of avian influenza viruses request pdf. The importance of swine was reemphasized because it has not only provided an environment for adaptive evolution during the avianhuman. It has therefore been suggested that influenza a virus exists in an evolutionary stasis in the reservoir species 2, 21.
The rapid evolution of influenza viruses the influenza a virus influenza virus type a fig. Influenza a virus an overview sciencedirect topics. Influenza experts have examined how the evolution of proteins found on the surfaces of flu viruses has impacted their ability to infect migratory birds and. The relative contribution of deterministic processes, such as selection, and stochastic processes, such as genetic drift, is influenced by the virus effective population size. The origins of the 2009 influenza a h1n1 pandemic in swine are unknown, highlighting gaps in our understanding of influenza a virus iav ecology and evolution. Predominant viruses h3, h6show a 2 year periodicity. In this thesis, the prevalence and transmission of avian influenza viruses aivs in 3 major bird groups duck, gull and murre were investigated to shed light on aiv ecology and evolution at this region. Host specificity is therefore a result of the interaction of numerous host factors with all viral proteins, among which, however, the polymerase. Historical perspective emergence of influenza a h1n1. This chapter discusses the ecology and evolution of avian influenza virus.
Further evidence that wild birds constitute a reservoir for influenza a virus comes from studies on viral evolution, which have shown limited evolution in wild ducks over time. A complete understanding of influenza virus evolution requires studies at all levels, as viral evolutionary dynamics may differ across spatial and temporal scales. Recently, influenza ah5n1 has developed into an epizootic of domestic poultry with associated human infections, observed first in hong kong in 1997, spreading throughout southeast asia over the following 7 years, and then extending to russia, europe, africa, the indian subcontinent and the middle east during the latter part of 2005 and early 2006. The ecology and adaptive evolution of influenza a interspecies. Influenza a virus evolution and spatiotemporal dynamics. Recently, extraordinarily reliable phylogenetic reconstructions of flu virus evolution have been made using samples from both extant and extinct strains.
Get a printable copy pdf file of the complete article 6. Influenza a viruses are pathogens of humans, horses, pigs, mink, seals, whales, and fowl. Influenza flu is a common infectious disease, but it is unusual in that the primary timescales for disease dynamics epidemics and viral evolution new variants are roughly the same. Influenza virus ecology, evolution, pathogenesis and public health impact. Pandemic influenza in humans is a zoonotic disease caused by the transfer of influenza a viruses or virus gene segments from animal reservoirs. We used wholegenome sequences collected as part of an intensive longterm eurasian wild bird surveillance study, and combined this genetic. Avian influenza virus aiv can infect a variety of avian species and mammals, leading to severe economic losses in poultry industry and posing a substantial threat to public health. Avian influenza virus ecology and evolution through a. Recently,extraordinarily reliable phylogenetic reconstructions of flu virus evolution have been made using samples from both extant and extinct. Evolutionary ecology of avian influenza and eid risk 3. The ecology of the virus is driven by numerous factors, including climate and avian migration patterns, yet relatively little is known about these drivers.
Pdf evolution and ecology of influenza a viruses researchgate. Factors responsible for the continuous persistence and evolution of low pathogenic avian influenza virus h9n2 volume 73 issue 4 m. While the global evolution of influenza a virus iav. The overall objective of this research line is to reduce the impact of epidemic and pandemic influenza through research on viruses in reservoir hosts, transient hosts, and humans, and to develop mitigation strategies based on surveillance, vaccines and antivirals.
Viral evolution is a subfield of evolutionary biology and virology that is specifically concerned with the evolution of viruses. The influenza viruses the medical journal of australia. Since 20, there have been several alarming influenza. Adaptive evolution and environmental durability jointly structure phylodynamic patterns in avian influenza viruses benjamin roche1,2, john m. All subtypes have been detected in isolates from avian species, and the evidence for the existence of a wild bird reservoir is. Phylogenetic analysis of the nucleotide sequence of influenza a virus rna segments coding for the spike proteins ha, na, and m2 and the internal proteins pb2, pb1, pa, np, m, and ns from a wide range of hosts, geographical regions, and influenza a virus. The ecology and evolution of influenza viruses request pdf. The evolutionary changes in the new hosts result from a number of processes including mutation. Coronavirus and influenza a virus outline coronavirus background sars outbreak cause of the 20022003 sars outbreak sarscov discovery, diagnostics, transmission origin of sarscov in humans influenza a virus background evolution and ecology pandemics past, present. Studies on the ecology of influenza aviruses established that all knowninfluenza aviruses are perpetuated in aquaticbirds, andahypothesiswasproposed59 thataquaticbirdsarethe primordial source of all influenza viruses in other species.
The patterns and processes of influenza virus evolution are of fundamental importance, underpinning such traits as the propensity to emerge in new host species and the ability to rapidly generate antigenic variation. In particular, the virus is found in birds as well as mammals including horses, pigs, and humans. The textbook of influenza is a comprehensive resource covering all aspects of influenza, from the genetic and molecular biology of the virus through to clinical aspects of the disease and the latest drug developments and treatments. Evolution of avian influenza examined sciencedaily. Influenza a viruses have been isolated from avian and mammalian hosts, although the primary. Avian influenza virus exhibits rapid evolutionary dynamics. The ecology and adaptive evolution of influenza a interspecies transmission. The evolutionary changes in the new hosts result from a number of processes including mutation, reassortment, and recombination.