This virus prefers cold weather and falling temperatures will test how good farm biosecurity really is, according to Dr Tom Burkgren of the American Association of Swine Veterinarians.

He added that the identification of the virus in Utah does raise concerns as it is unclear how the virus arrived there within the last month. Utah is the 31st US state to report a PED-positive result.

There has been no sign of an increase in the reporting of PED-positive samples in the US so far. Neither have there been any new cases of Swine Porcine Delta Corona virus in the US for two weeks either.

Canada has not reported any new PED cases for two months and a veterinarian with Ontario Pork reports that, since April, there have been very few incidents of environmental contamination from the virus in the province.

With the drop in PED cases, the Agricultural Institute of Colombia has reopened the country's borders for the import of breeding pigs from the United States and Canada, which had been restricted due to previous PED outbreaks.

Earlier this year, pork prices to producers shot up in the US as PED outbreaks – which have caused the deaths of an estimated eight million pigs there – were expected to leave the domestic and world markets short of pig meat.

With feed prices moderate, pig producers in the US have grown their pigs to heavier weights, leading to just a modest reduction in US pig meat production. And, of course, Russia has banned imports of meat from the US, Canada and elsewhere.

October hogs closed down $2.12 at $102.97, which another market analyst, Jim Wyckoff, thinks may signal lower prices in the near term.

Interestingly, US retail pork prices set new records last month. Market analysts at the University of Missouri report that the average price of a pound of pork in grocery stores during August was $4.20 – 7.3 cents higher than the month before and 44.3 cents higher than in August 2013. It was the sixth consecutive month with a new retail price record for pork.