Influenza-A infections in animals and birds and their significance in the epidemiology of human influenza-A

Abstract

The objective of this presentation is to point out at knowledge obtained so far through comparative analyses of the influenza-A virus, certain ecological and epizootiological aspects, and at the cases registered so far of the transfer of this virus among animals, animals and birds and humans. In this way, we believe we will help our professional public to take a more comprehensive view of the currently uncertain epizootiological (epidemiological) situation regarding infections with influenza-A viruses in the world, and to secure preventive measures with due attention. New information is daily added to this matter, which is of wide-ranging aspects and, because of insufficient space, we have limited this work to the aspects which, because of insufficient space, we have limited this work to the aspects which are currently biologically the most significant. Consequently we have divided the entire presentation into the following sections Introduction with emphasis on the existence of large numbers of influenza-A viruses in nature, with a wide range of antigenic and biological characteristics in domestic and wild animals and birds, as well as on the fact that these viruses can be a potential source of so-called new pandemic viruses and pose a constant threat to human welfare. Results of comparative analyses of the influnza-A virus, with special emphasis on classification virion structure, genome structure and nomenclature, on the progressive mutation of the virus, known as antigenic drift, and the genetic recombination, known as antigenic shift. Influenza-A viruses in humans animals and birds with a presentation of subtypes and variants of the virus identified so far. Transfer of the virus among animals, birds and humans with a presentation of cases registered so far of virus transfer in nature as well as possibilities for experimental infections of calves, swine, mice hamsters, and squirrels with influenza-A viruses originating from birds. Concluding remarks indicate the need for veterinary medicine to be more intensely engaged on investigations of the biology, genetics and epizootiology of isolated viruses in animal and birds, and thus to contribute to the clarification of numerous unknown factors that render influenza epidemiology in humans so exceptional. References show a part of the literature used in preparing this presentation.