Avian Influenza Virus Surveillance in Wild Birds in Georgia: 2009-2011

The Caucasus, at the border of Europe and Asia, is important for migration and over-wintering of wild waterbirds. Three flyways, the Central Asian, East Africa-West Asia, and Mediterranean/Black Sea flyways, converge in the Caucasus region. Thus, the Caucasus region might act as a migratory bridge for influenza virus transmission when birds aggregate in high concentrations in the post-breeding, migrating and overwintering periods. Since August 2009, we have established a surveillance network for influenza viruses in wild birds, using five sample areas geographically spread throughout suitable habitats in both eastern and western Georgia. We took paired tracheal and cloacal swabs and fresh feces samples. We collected 8343 swabs from 76 species belonging to 17 families in 11 orders of birds, of which 84 were real-time RT-PCR positive for avian influenza virus (AIV). No highly pathogenic AIV (HPAIV) H5 or H7 viruses were detected. The overall AIV prevalence was 1.6%. We observed peak prevalence in large gulls during the autumn migration (5.3-9.8%), but peak prevalence in Black-headed Gulls in spring (4.2-13%). In ducks, we observed increased AIV prevalence during the autumn post-moult aggregations and migration stop-over period (6.3%) but at lower levels to those observed in other more northerly post-moult areas in Eurasia. We observed another prevalence peak in the overwintering period (0.14-5.9%). Serological and virological monitoring of a breeding colony of Armenian Gulls showed that adult birds were seropositive on arrival at the breeding colony, but juveniles remained serologically and virologically negative for AIV throughout their time on the breeding grounds, in contrast to gull AIV data from other geographic regions. We show that close phylogenetic relatives of viruses isolated in Georgia are sourced from a wide geographic area throughout Western and Central Eurasia, and from areas that are represented by multiple different flyways, likely linking different host sub-populations

Influenza A Viruses in Wild Birds of the Pacific Flyway, 2005–2008

Avian influenza viruses (AIVs) pose a significant threat to public health, and viral subtypes circulating in natural avian reservoirs can contribute to the emergence of pathogenic influenza viruses in humans. We investigated the prevalence and distribution of AIVs in 8826 migratory and resident wild birds in North America along the Pacific flyway, which is a major north–south migration pathway that overlaps with four other flyways in Alaska providing opportunities for mixing of Eurasian and American origin influenza viruses. Overall, the prevalence of AIVs was low (1%) among the wide range of avian species tested, but we detected AIVs in 69 hunter-harvested waterfowl (Anseriformes) sampled at a national wildlife refuge in California from October 2007 to January 2008. A wide range of subtypes were detected in waterfowl with H6N1, H10N7, H7N3, and H3N5 being the most common. We suspect H6N1 was introduced or remerged in 2007 at this key wintering site for waterfowl along the Pacific Flyway. Over a 3-week period, 13 H6N1 AIVs were isolated from two northern pintails (Anas acuta), three northern shovelers (Anas clypeata), three ring-necked ducks (Aythya collaris), four American widgeon (Anas americana), and one gadwall (Anas strepera). We conclude that a diverse array of AIVs was present and that cross-species transmission was occurring among waterfowl in the central valley wetlands of California