Trypsin is required in the hemagglutinin (HA) cleavage to in vitro influenza viruses activation. This HA cleavage is necessary for virus cell entry by receptor-mediated endocytosis. Bacteria in the respiratory tract are potential sources of proteases that could contribute to the cleavage of influenza virus in vivo. From 47 samples collected from horses, pigs, and from humans, influenza presence was confirmed in 13 and these samples demonstrated co-infection of influenza with flagellated bacteria, Stenotrophomonas maltophilia from the beginning of the experiments. Despite treatment with antibiotics, the bacteria remained resistant in several of the co-infected samples (48.39%). These bacteria, considered opportunistic invaders from environmental sources, are associated with viral infections in upper respiratory tract of hosts. The protease (elastase), secreted by Stenotrophomonas maltophilia plays a role in the potentiation of influenza virus infection. Proteolytic activity was detected by casein agar test. Positive samples from animals and humans had either a potentiated influenza infectivity or cytopathic effect (CPE) in MDCK and NCI H292 cells, Stenotrophomonas maltophilia were always present. Virus and bacteria were observed ultrastructurally. These in vitro findings show that microbial proteases could contribute to respiratory complications by host protease activity increasing inflammation or destroying endogenous cell protease inhibitors.

Birds are the most important reservoirs of the influenza virus. Its maintenance in its natural hosts, including man, allows the influenza virus to reassorts its strains. The recent report of an avian influenza A (H5N1) virus in humans, was in a child with fatal respiratory illness in China, 1997. The current study was conducted to elucidate the transportation of the influenza by birds that migrate, annually, through the both Northern and Southern hemispheres, with special attention paid to the Vireo olivaceus [Juruviara(BR) or Red-eyed vireo(USA)] species, which travels from the USA to Brazil, and vice versa, and the Elaenia mesoleuca [Tuque(BR) or (USA)] species that flies over the entire Southern Hemisphere. There are two species of birds, which breed and migrate in São Paulo State, Brazil, and which were demonstrated to carry Influenza virus, were selected. The viral particles isolated were observed by electron microscopy. The influenza virus was detected by the House Duplex/PCR and Gloria molecular biology tests. The results demonstrated that the Elaenia mesoleuca and Vireo olivaceus bird species are carrying the Influenza virus whilst crossing both the Northern and Southern hemispheres. To understand the role that these migrating birds may play in epidemic influenza, in Brazil, characterization of avian influenza subtypes will be done.

85.29% and 91.17%, respectively. These sera also presented higher percentages (97.05%) of antibodies to specific strains isolated from some of the positive pigs. These data reveal that numerous different influenza virus strains, detected in the Brazilian pig populations, were probably introduced by avians or even through humans, during swine husbandry practices.

High levels of antibodies against the human influenza A(H 1 N 1 ) and A(H 3 N 2 ) strains in horse sera have been reported. The aim of the present study was to survey the human influenza virus strains present in horses using two methodologies, viral isolation and serology.Sera and swabs (oro-nasal) were collected from horses belonging to stud and racing stables

No abstract