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Commentary
Fujian H5N2 Confirmations Accelerate In US
Midwest
Recombinomics Commentary
April 3, 2015 10:15
The above table from the APHIS April 2 update on avian influenza includes the 4 locations where H5N2 was confirmed on April 2. The table shows the dramatic acceleration in detections, as wild birds increase migration north through the Midwest. The 12 confirmations began on March 4, followed by one wave between March 9-13 (4 outbreaks in 3 states) and another wave between March 27 to April 2 (6 outbreaks in 3 states, with a concentration in Minnesota) - see H5N2 map.
Minnesota is the largest producers of domestic turkeys, which now has 5 confirmed farms in 4 counties. The detection on March 4, five days before the March 9-13 wave led to media reports citing “experts” who claimed that the initial cases signaled a movement from north to south or west to east, which were inconsistent with wild bird migration patterns. However, these “jumps” and interpretations were heavily dependent on the absence of wild bird reports in the Midwest, where surveillance was in the routine mode.
In contrast, and enhanced surveillance mode in western states confirmed Fujian clade 2.3.4.4 H5 in 49 wild birds (H5N8, H5N2, H5N1) with collection dates in December and January. The new cases in the administrative Pacific Flyway abruptly ended in January when hunting season ended, because the surveillance large targeted hunter killed birds which were swabbed within 24 hours of death. The number of confirmations continued after the hunting season ended because confirmations were delayed and the “new” confirmations were of samples collected during hunting season, but reported at the APHIS site and in OIE reports when confirmed.
The APHIS table included collection dates, but the OIE reports only cited the confirmation dates, which was used to represent the start of the outbreak, which led to the appearance of new infections in February and March.
Although there have been no new cases reported in the Pacific Flyway, the above list of farms, as well as captive falcons confirmed on March 27, signals the presence of H5N2 in the Central and Mississippi Flyways, which may trace back to 2014 when the wild birds recently fed to the captive falcons were killed, highlighting the limitations of routine surveillance. Recent testing of fecal samples from resident birds in Minnesota produced a low frequency of influenza A positives, raising degradation concerns, and results on testing of 150 hunter killed snow birds in Iowa have not been released.
However, the explosion of outbreaks on farms suggests the wave depicted in the above table will continue and may accelerate due to peak migration in April, which will extend into Canada.
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