# 2406
When we think about birds that might carry avian influenza, we generally focus on aquatic species. In birds, influenza is primarily a gastrointestinal infection, and it is transmitted via infected feces passed into shared water environments.
Of course, we do know that non-water birds can become infected. We need only look at the reports from Hong Kong these past few years, where they've detected the H5N1 virus in a variety of non-aquatic species including House Crows and Magpie Robins.
Despite these reports, most monitoring and surveillance is done on water birds, like ducks, egrets, and swans.
A study appears in this month's Journal of Emerging Infectious Diseases which looks at the prevalence of influenza A infection in non-water birds in China.
Townsend Peterson A, Bush SE, Spackman E, Swayne DE, Ip HS. Influenza A virus infections in land birds, People's Republic of China. Emerg Infect Dis [serial on the Internet]. 2008 Oct [date cited]. Available from http://www.cdc.gov/EID/content/14/10/1644.htm
DOI: 10.3201/eid1410.080169
The authors of this report spent three years taking samples from nearly 1000 land birds in central and southern China (see figure 1). They found 24 land birds, or roughly 2.3%, carrying the Influenza A virus.
Figure 1
Migratory birds were more than twice as likely (4.8%) to carry the influenza A virus as were non-migratory birds (1.8%).
None of these birds tested positive for the H5 virus (by PCR), although the authors admit that the method they used to preserve the samples prevented `virus isolation or full, strain-level characterization of influenza viruses'.
Here is the abstract and opening paragraphs to the study, slightly reparagraphed and highlighted to improve readability.
Dispatch
Influenza A Virus Infections in Land Birds, People's Republic of China
A. Townsend Peterson,
Sarah E. Bush, Erica Spackman, David E. Swayne, and Hon S. Ip
Author affiliations: University of Kansas, Lawrence, Kansas, USA (A.T. Peterson, S.E. Bush); US Department of Agriculture, Athens, Georgia, USA (E. Spackman, D.E. Swayne); and US Geological Survey, Madison, Wisconsin, USA (H.S. Ip)
Abstract
Water birds are considered the reservoir for avian influenza viruses. We examined this assumption by sampling and real-time reverse transcription–PCR testing of 939 Asian land birds of 153 species.
Influenza A infection was found, particularly among migratory species. Surveillance programs for monitoring spread of these viruses need to be redesigned.
Avian influenza virus ecology has long regarded waterbirds as a primary reservoir. Although the benchmark study detailed prevalences across all taxa (1), subsequent studies have focused exclusively on waterbirds (2) with few exceptions (3,4).
We reexamined these assumptions on the basis of a broad sampling of bird diversity in Southeast Asia, where bird-borne influenza viruses are of particular concern (5). We sampled and tested diverse land birds for influenza A virus infection and showed that land birds also harbor infections with these viruses.
Birds in these taxa are not irrelevant in virus transmission and should form an integral part of avian influenza surveillance and monitoring programs.
The entire study may be read online. The authors conclude by saying that their findings indicate that land birds need to be included in future surveillance for avian influenza infections.
We have taken a step toward a more complete understanding of influenza virus ecology among wild birds. Our partial survey of influenza virus distributions across the rich avifaunas of the southern region of China demonstrated frequent infections.
This result contrasts with the current dogma in the influenza surveillance community. We suggest that to be effective future surveillance efforts will need to include the full diversity of wild birds.
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