http://www.virologyj.com/content/12/1/151/#B14
Wild bird surveillance for highly pathogenic avian influenza H5 in North America

Paul L. Flint1*, John M. Pearce1, J. Christian Franson2 and Dirk V. Derksen1
Author Affiliations
1 U.S. Geological Survey, Alaska Science Center, Anchorage, AK, USA
2 U.S. Geological Survey, National Wildlife Health Center, Madison, WI, USA

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Virology Journal 2015, 12:151 doi:10.1186/s12985-015-0377-2
The electronic version of this article is the complete one and can be found online at: http://www.virologyj.com/content/12/1/151
Received: 29 May 2015
Accepted: 7 September 2015
Published: 28 September 2015
? 2015 Flint et al.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.


Abstract

It is unknown how the current Asian origin highly pathogenic avian influenza H5 viruses arrived, but these viruses are now poised to become endemic in North America. Wild birds harbor these viruses and have dispersed them at regional scales. What is unclear is how the viruses may be moving from the wild bird reservoir into poultry holdings. Active surveillance of live wild birds is likely the best way to determine the true distribution of these viruses. We also suggest that sampling be focused on regions with the greatest risk for poultry losses and attempt to define the mechanisms of transfer to enhance biosecurity. Responding to the recent outbreaks of highly pathogenic avian influenza in North America requires an efficient plan with clear objectives and potential management outcomes.

Background

The original United States interagency strategic plan for detection of Asian highly pathogenic H5N1 avian influenza was developed nearly a decade ago, with focus on the early detection of an exotic virus [1]. The current outbreaks of HPAI H5N8 and H5N2, caused by foreign origin viruses, have very quickly become widely distributed within North America, thus negating the need for early detection at the broad scale. Two new avian influenza surveillance and monitoring documents have been recently released that address early detection at local and regional scales. One focuses on detection of HPAI in waterfowl in high priority watersheds and the spread of viruses to new areas of concern [2]. The other encompasses a strategy for early detection of avian influenza viruses of significance in wild birds in general, and encourages sampling of areas with high poultry density [3]. We propose taking these plans a step further by suggesting a 2-tiered surveillance strategy focusing on waterfowl and bridge species in the vicinity of poultry operations. This 2-step sampling design would address the mechanism(s) of virus transfer and provide data that can inform management actions that minimize the impact of these viruses on domestic poultry.

Main text

It is unknown how HPAI H5 viruses from Asia reached North America [4]?[7]. Asian origin HPAI H5 viruses were first detected in North America in November of 2014 in poultry farms along the Fraser River in southwestern Canada but it is unknown how these viruses were introduced [8]. Extensive sampling for the Asian HPAI H5N1 from 2006-2010 failed to reveal evidence of intact foreign avian influenza (AI) viruses in North American wild birds [9]. However, numerous AI viruses isolated from wild birds in North America were shown to contain individual genes that originated in Asia leading to the conclusion that wild birds do transfer viruses among continents, although these viruses appear to be reassorted into the local AI community [10]?[12]. Thus, the detection in November of 2014 of a non-reassorted AI virus in North America [13] is unusual, although not unprecedented [14]. Further sampling in early 2015 confirmed that the Asian origin HPAI H5N8 subsequently reassorted with endemic viruses into at least two different HPAI subtypes, H5N2 and H5N1 [7], [8]. Thus, within a small geographic area and a short period of time, HPAI H5 viruses of foreign origin were identified in both poultry and wild birds in western North America. A key question involves the transmission pathway. Does this represent long distance-intercontinental dispersal of HPAI H5N8 by wild birds with subsequent transmission to poultry [6]? Alternatively, were the viruses introduced directly into poultry from an unknown source with subsequent dispersal into wild birds? Given the available data, both mechanisms are plausible and we cannot distinguish between these competing hypotheses...
Full text at link. Conclusions section has suggestions for the direction of future sampling.

This event still may be unprecedented in the sense that the reference for a precedent is about H7N9, an LPAI virus - http://www.fao.org/ag/againfo/progra.../Virology.html - The H5 viruses are HPAI, as stated in the USGS paper.