Avian flu has wiped out more than 50 million chickens, turkeys and other poultry in the U.S. this year, making it the worst animal-health disaster to date and topping losses in the 2015 avian flu outbreak.
It might have been worse had not producers increased biosecurity after the outbreak seven years ago.
In 2015, about 30 per cent of the cases were traced directly to wild bird origins, compared to 85 per cent this year, said the USDA.
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As of the end of November, there had been 136 premises and 4.4 million birds affected by avian influenza in Canada, with Alberta accounting for roughly one-third of those totals, according to the Canadian Food Inspection Agency.
[RELATED] Alberta bears brunt of avian influenza outbreak
Almost all the Alberta cases occurred during a four-week period in April-May or in the fall. There were four reported cases in November, two in commercial flocks.