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Commentary
CIDRAP Media Myth On Fujian H5 Transmission By
Wild Birds
Recombinomics Commentary
March 30, 2015 18:00
Referring to the mixing of H5N8 with North American viruses, he said, "Why do we make the jump to wild ducks to explain this? Reassortment could also occur in a backyard flock of domestic ducks after a more direct introduction [of H5N8] via people." He suggested that travelers could possibly have brought the virus to Canada from Asia.
The above comments from a CIDRAP report entitled “Role of wild birds in US H5N2 outbreaks questioned” are unfortunate. When H5N2 was confirmed in multiple locations in the Midwest (Pope County, Minnesota; Jasper and Moniteau Counties, Missouri; Boone County, Arkansas; Leavenworth County, Kansas), some media reports questioned the role of wild birds because of speculation that the confirmation of H5N2 in Minnesota 5 days prior to the multiple detections in states to the south signaled movement from north to south. Geographic jumps inconsistant with migration routes were also cited for the appearance in the Midwest after detections in the US northwest. Moreover, as quoted above, there was an absence of wild bird positives prior to the H5N2 commercial farm outbreak in British Columbia.
However, all of these observations are link to surveillance issues.
After H5N2 HPAI was confirmed in Canada, the USDA increased surveillance and samples collected 4 days after the Canada OIE report were positive for H5N2 in a northern pintail at Wiser Lake, 7 miles from Fraser Valley, and H5N8 in captive gyrfalcons that died after being fed a wigeon captured near Wiser lake. Later that month a sample was collected from a hunter killed green-winged teal near Suma, 5 miles from the Canadian, which was positive for H5N1.
Sequence analysis showed the H5N8 was derived from the H5N8 that caused a large outbreak in early 2014 in South Korea (but was most closely related to a crane sequence from Japan in late 2014, A/crane/Kagoshima/KU1/2014). This H5N8 was the parental source for H5N2 and H5N1, which had North American wild bird flu segments in association with H5N8 (at ratios of 3 to 5 and 4 to 4, repectively).
The detection of H5N1 in the wild bird preceded detection of H5N1 in Fraser Valley at a backyard farm, and early detection in wild birds also applied to the first two reported commercial farms in the United States, which were in California.
The enhanced surveillance confirmed Fujian H5 (H5N8, H5N2, H5N1) in 49 wild birds. Seven of the positives were in California. All were H5N8 and preceded the detection in the commercial farms. The wild birds were in four counties (Butte, Yolo, Colusa, Solano) all to the north of the counties of the commercial farms (Stanislaus and Kings – see H5N8 map).
However, the enhanced surveillance was limited to the administrative Pacific Flyway during the hunting season and most positives were from hunter killed birds. When the hunting season ended, new positives abruptly ended (new confirmations were limited to samples collected during hunting season, which lately have been confirmed 2-3 months post-collection).
Thus, in the absence of enhanced surveillance, Fujian H5 was silently spreading through the Midwest to the Gulf of Mexico states for the winter. Now, as these birds begin migrating north, farms are infected, especially turkey farms which are more susceptible.
Last week the first confirmation of Fujian H5 was made using routine surveillance. A Canada goose near Cheyenne, Wyoming had neurological symptoms and tested positive (see H5N2 map). Collection of a live sample during routine surveillance is unusual. Most surveillance involves limited testing on dead birds or feces, where viral RNA rapidly degrades.
The quotes cited above are heavily dependent of poor routine surveillance.
The claim of a lack of wild bird involvement was also cited in the H5N8 spread in Europe in November, 2014. Sequences were closely related to those from early 2014 in South Korea, as well as sequences from Japan in late 2014. However, wild birds in South Korea and Japan fly to Russia for the summer and Russia had not reported H5N8, so an absence of a migratory direct linked between birds in South Korea / Japan and those in Western Europe was used to claim that the spread was due to humans.
However, on December 25 Russia announced the detection of H5N8 in a hunter killed wigeon, A/wigeon/Sakha/1/2014, that had been shot in September, providing the wild bird link for moving the H5N8 from South Korea / Japan to Russia for the summer and then to South Korea / Japan or western Europe in the fall.
Thus, the data for wild bird transmission of H5N8 and derivatives in Europe, Asia (including a massive outbreak in Taiwan), and North America are overwhelming, scientists who are experts at confusing media on the role of wild birds on H5 transmission notwithstanding.
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