[Anthropozoonozes: the species barrier].
Various animal virus can infect humans with a wide range of clinical manifestations from subclinical to fatal. In theory transmission is also possible in a number of poorly defined situations. Several examples of interspecific contamination in animals and the emergence of new viral infections in animals have documented the ability of some viruses to cross the species barrier. The barrier concept is based on epidemiological factors lowering the probability of exposition to risk and molecular factors limiting or preventing viral replication in alien hosts. Although these mechanisms are generally effective, they can fail under circumstances. This is notably the case when changes in the ecosystem lead to the development of variants able to replicate in different hosts including man. An analysis of several mechanisms underlying the species barrier is also presented. Some viruses are prevented from entering the organism by the absence of suitable receptors, but development is possible if entrance is forced. Other viruses can enter but the organism but are unable to complete their developmental cycle. Study has shown that these inhibitory mechanisms correspond to interactions involving a small number of amino acids. Such a blockage could be leaky, especially for RNA viruses with a high mutation rate.
Eloit
M
M
L'Unité Mixte de Recherche 955, Génétique Moléculaire et Cellulaire, Génétique Virale, Institut National de la Recherche Agronomique, Ecole Nationale Vétérinaire, Maisons Alfort, France. eloit@vet-alfort.fr
D000818:Animals; D017753:Ecosystem; D004781:Environmental Exposure; D006801:Humans; D009154:Mutation / Q000235:genetics; D012328:RNA Viruses / Q000235:genetics / Q000502:physiology; D012307:Risk Factors; D013045:Species Specificity; D014777:Virus Diseases / Q000276:immunology / Q000635:transmission*; D014779:Virus Replication / Q000502:physiology; D015047:Zoonoses / Q000635:transmission / Q000821:virology*