Reasons why avian influenza spread so fiercely across the United States, but not in Canada, are coming clear from recent research.
There was immediate and strict biosecurity in Ontario and British Columbia that contained outbreaks in late 2014 and in June of 2015.
In Minnesota, by comparison, some of the dead turkeys were trucked out by rendering companies, potentially spreading the virus along their routes.
In Canada, flocks were kept inside their barns under strict quarantine, euthanized and composted to kill the virus which cannot withstand heat.
A University of Minnesota study says farmers who actively tilled fields near turkey barns in the early days of last year's bird flu outbreak may have unwittingly helped spread the virus.
The Center for Animal Health and Food Safety says soil in those fields may have been contaminated with droppings from migrating ducks and geese which were the likely source of the highly pathogenic H5N2 virus.
The report says the virus can survive cold soil temperatures, and tilling may have created airborne particles that could carry the virus.
Minnesota Public Radio reports the authors urge caution, saying their findings should be viewed as "hypothesis-generating rather than confirmatory" and that more research is needed.