Persistence of Highly Pathogenic Avian Influenza Viruses in Natural Ecosystems

摘要

Understanding of ecologic factors favoring emergence and maintenance of highly pathogenic avian in. uenza (HPAI) viruses is limited. Although low pathogenic avian in-. uenza viruses persist and evolve in wild populations, HPAI viruses evolve in domestic birds and cause economically serious epizootics that only occasionally infect wild popula-tions. We propose that evolutionary ecology considerations can explain this apparent paradox. Host structure and trans-mission possibilities differ considerably between wild and domestic birds and are likely to be major determinants of virulence. Because viral fi tness is highly dependent on host survival and dispersal in nature, virulent forms are unlikely to persist in wild populations if they kill hosts quickly or affect predation risk or migratory performance. Interhost transmis-sion in water has evolved in low pathogenic in. uenza vi-ruses in wild waterfowl populations. However, oropharyn-geal shedding and transmission by aerosols appear more effi cient for HPAI viruses among domestic birds