Winker K, McCracken KG, Gibson DD, Pruett CL, Meier R, Huettmann F, et al. Movements of birds and avian influenza from Asia into Alaska. Emerg Infect Dis [serial on the Internet]. 2007 Apr [date cited]. Available from
Abstract
Asian-origin avian influenza (AI) viruses are spread in part by migratory birds. In Alaska, diverse avian hosts from Asia and the Americas overlap in a region of intercontinental avifaunal mixing. This region is hypothesized to be a zone of Asia-to-America virus transfer because birds there can mingle in waters contaminated by wild-bird–origin AI viruses. Our 7 years of AI virus surveillance among waterfowl and shorebirds in this region (1998–2004; 8,254 samples) showed remarkably low infection rates (0.06%). Our findings suggest an Arctic effect on viral ecology, caused perhaps by low ecosystem productivity and low host densities relative to available water. Combined with a synthesis of avian diversity and abundance, intercontinental host movements, and genetic analyses, our results suggest that the risk and probably the frequency of intercontinental virus transfer in this region are relatively low.
The article has a good synopsis of why anyone would be interested in Alaska for the study of pandemic avian influenza (of any type). The data also add to the work on whether wild birds or domestic birds would have a greater influence on bird to human exposures to the H5N1 avian flu. The article is also an easily accessed scientific paper to study for its structure of presenting information and interpretations of data (but the data themselves are not included). I wish the studies had included stable nuclide analyses for examining natural variation in environmental chemistry (and in tracing the species and human food webs), but no one asked ;0)
See previous
- Scientists Criticize Bird Flu Search -
http://ykalaska.wordpress.com/2006/12/05/scientists-criticize-bird-flu-search/
We found low rates of infection among the 8,254 samples obtained from the most important host groups, waterfowl (Anatidae) and shorebirds (Charadriidae and Scolopacidae; Appendix Table). From these samples we obtained only 5 isolates, which represent an infection rate of just 0.061%. These isolates included hemagglutinin subtypes H3, H4, and H6. The 5 isolates were found in 3 (0.2%) of 1,477 green-winged teal (Anas crecca), 1 (0.76%) of 131 mallards (Anas platyrhynchos), and 1 (0.03%) of 3,703 northern pintails (Anas acuta). We found neither evidence of a clearly Eurasian origin for any of the virus genes sequenced from these Alaska isolates nor H5 subtypes. Our data do show a remarkably close genetic association between avian influenza (H6) virus in Alaska ducks and a poultry outbreak in California in nucleoprotein and nonstructural protein A genes. This finding reflects real-time connections of migratory ducks between Alaska and California, and this vector connection extends into the Russian Far East These findings affirm the intracontinental importance and risk posed by this region…
The infection rates we found are substantially lower than those found for interior Alaska… Aerial surveys of waterfowl across Alaska show more ponds and fewer ducks per unit area on tundra; the number of ducks per pond on tundra habitat is less than half the number found in the boreal-forest dominated interior. This … resulting in the dilution of virus in waters with fewer available hosts, may in part explain our results. This is the first geographically and taxonomically extensive Arctic AI surveillance in North America, and it suggests that some Arctic effect lowers infection rates, thus lowering the risk of intercontinental viral transfer in these high-latitude regions…
[while the current Arctic and sub-Arctic regions may result in a lower population density of birds and their shed viruses (and also people) it is the lower density and not the "Arctic" per se which affects the infection rate of the virus. However, the lower density may be only of the birds. Other research [cited here, | flu viruses survive tundra ponds | and here, | Frozen fecal bird flu types |] has shown that the viruses may survive in ponds between breeding seasons (over winter) and thus might accumulate or become more concentrated in numbers. As we know from disease ecology and biocultural anthropology, the disease process involves several factors besides presence and abundance of the infective microorganism. mpb]
Human population densities in Alaska are relatively low, especially in the Beringian Crucible, and Alaska lacks a large agricultural sector. However, mammalian carnivores abound and could be susceptible hosts. Direct human infection from wild birds is possible, but transmission from birds to humans is difficult. Nevertheless, exposure in this region may be considerable; hunters kill ≈99,000 waterbirds for food each year on the Yukon-Kuskokwim Delta alone.
I knew the testing for bird flu was earlier than last March when the program was publicized, but hadn’t known it was 9 years old.
…We obtained our baseline data on viruses and vectors by screening wild birds for AI virus in western Alaska, starting in 1998. We focused on western Alaska because of the unparalleled overlap of Old World and New World bird migration systems in this region. To estimate the risk of Asian-origin AI viruses being delivered by migratory birds to North America through Alaska, we evaluated AI virus infection rates, bird movements, and the diversity and degree of intercontinental host overlap…
There is a table with “Species of waterfowl (Anatidae) and shorebirds (Charadriidae, Recurvirostridae, and Scolopacidae) in Alaska with an Old World connection or from which cloacal swabs or fecal samples were obtained, Alaska, 1998–2004″ but once again, there are no results of these samples and no identification of where the samples came. I’ll list the bird names in a comment when I can get them.
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