title: Birds and viruses at a crossroad--surveillance of influenza A virus in Portuguese waterfowl.
abstract: During recent years, extensive amounts of data have become available regarding influenza A virus (IAV) in wild birds in northern Europe, while information from southern Europe is more limited. Here, we present an IAV surveillance study conducted in western Portugal 2008-2009, analyzing 1653 samples from six different species of waterfowl, with the majority of samples taken from Mallards (Anas platyrhynchos). Overall 4.4% of sampled birds were infected. The sampling results revealed a significant temporal variation in the IAV prevalence, including a pronounced peak among predominantly young birds in June, indicating that IAV circulate within breeding populations in the wetlands of western Portugal. The H10N7 and H9N2 subtypes were predominant among isolated viruses. Phylogenetic analyses of the hemagglutinin and neuraminidase sequences of H10N7, H9N2 and H11N3 virus showed that sequences from Portugal were closely related to viral sequences from Central Europe as well as to IAVs isolated in the southern parts of Africa, reflecting Portugal's position on the European-African bird migratory flyway. This study highlights the importance of Portugal as a migratory crossroad for IAV, connecting breeding stationary waterfowl with birds migrating between continents which enable transmission and spread of IAV.
authors.affiliation: Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnæus University, Kalmar, Sweden.
authors.forename: Conny
authors.initials: C
authors.lastname: Tolf
authors.forename: Daniel
authors.initials: D
authors.lastname: Bengtsson
authors.forename: David
authors.initials: D
authors.lastname: Rodrigues
authors.forename: Neus
authors.initials: N
authors.lastname: Latorre-Margalef
authors.forename: Michelle
authors.initials: M
authors.lastname: Wille
authors.forename: Maria Ester
authors.initials: ME
authors.lastname: Figueiredo
authors.forename: Monika
authors.initials: M
authors.lastname: Jankowska-Hjortaas
authors.forename: Anna
authors.initials: A
authors.lastname: Germundsson
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Duby
authors.forename: Camille
authors.initials: C
authors.lastname: Lebarbenchon
authors.forename: Michel
authors.initials: M
authors.lastname: Gauthier-Clerc
authors.forename: Björn
authors.initials: B
authors.lastname: Olsen
authors.forename: Jonas
authors.initials: J
authors.lastname: Waldenström
mesh_terms: D025041:Animal Migration; D000818:Animals; D000835:Animals, Wild / Q000235:genetics / Q000821:virology; D001717:Birds / Q000821:virology*; D005260:Female; D057921:Influenza A Virus, H10N7 Subtype / Q000235:genetics / Q000302:isolation & purification*; D053127:Influenza A Virus, H9N2 Subtype / Q000235:genetics / Q000302:isolation & purification*; D005585:Influenza in Birds / Q000453:epidemiology / Q000821:virology*; D010802:Phylogeny; D011174:Portugal / Q000453:epidemiology