Since the central theme of this book is the transmission of disease agents through the food chain, we will examine influenza viruses from this perspective. Influenza A viruses are found in humans, pigs, horses, sea mammals, and also in wild aquatic and domestic birds [23]. How are they spread? Between mammals, influenza is an airborne infection, but between birds, influenza can be either an airborne or waterborne infection. Influenza viruses of aquatic birds periodically transmit to domestic birds sometimes with catastrophic effects; this transmis­ sion can be either airborne or waterborne. Less frequently, avian influenza viruses transmit to mammals and three to four times in the past century this transmission has initiated a pandemic of influenza in humans. The method of spread of avian influenza viruses to mammals remains unresolved, but could be either airborne or waterborne. In this report we will consider recent examples of interspecies transmission of influenza A viruses and the possible prevention of emergence of the next human pandemic which is considered imminent. The reservoirs of influenza A viruses The available evidence indicates that aquatic birds are the reservoirs of all 15 subtypes of influenza A viruses. We will first consider the replication of influenza A in aquatic birds. In wild ducks, influenza viruses replicate preferentially in the cells lining the intestinal tract, cause no disease signs, and 8 7 are excreted in high concentrations in the feces (up to 10 .

Inhalt

Cowpox: a re-evaluation of the risks of human cowpox based on new epidemiological information.- Characterization of a cowpox-like orthopox virus which had caused a lethal infection in man.- Molecular genetic analyses of parapoxviruses pathogenic for humans.- Recent advances in molluscum contagiosum virus research.- Molecular anatomy of lymphocystis disease virus.- Detection of virus or virus specific nucleic acid in foodstuff or bioproducts - hazards and risk assessment.- Rapid molecular detection of microbial pathogens: breakthroughs and challenges.- Where do we stand with oral vaccination of foxes against rabies in Europe?.- Foot-and-mouth disease as zoonosis.- Molecular epidemiology of influenza.- Influenza virus: transmission between species and relevance to emergence of the next human pandemic.- Functional chimeric HN glycoproteins derived from Newcastle disease virus and human parainfluenza virus-3.- Viral factors determining rotavirus pathogenicity.- Viral zoonoses and food of animal origin: caliciviruses and human disease.- The role of human caliciviruses in epidemic gastroenteritis.- Clinical similarities and close genetic relationship of human and animal Borna disease virus.- Molecular characterization of Borna disease virus from naturally infected animals and possible links to human disorders.- Haemorrhagic fevers and ecological perturbations.- Transmission, species specificity, and pathogenicity of Aujeszky's disease virus.- The role of veterinary public health in the prevention of zoonoses.- Viral infections transmitted by food of animal origin: the present situation in the European Unio.- Viral zoonosis from the viewpoint of their epidemiological surveillance: tick-borne encephalitis as a model.- Strategies to avoid virus transmissions by biopharmaceutic products.