The USDA’s Animal and Plant Health Inspection Service (APHIS) has released a root cause investigation report that identified reuse of contaminated flexible intermediate bulk containers (FIBCs), also known as tote bags, as the most likely cause for how the swine enteric coronavirus disease (SECD) viruses -- including porcine epidemic diarrhea (PED) virus and swine delta coronavirus -- entered the United States. 

APHIS examined seventeen potential root cause scenarios, looking to see if they meet all four criteria needed to bring the virus from an overseas location to U.S. pig farms, as well as if there was evidence to support the scenario. 

While the investigation did not uncover definite proof for any route of entry, a small number of scenarios were deemed plausible, with reuse of FIBCs being determined as the scenario that best fit the criteria for virus entry into the U.S.

FIBCs are commonly used to transport many types of material including sand for flood control, soybeans, pet treats, or almost any kind of bulk material. They are designed to be reused.  It is not a common practice to clean and disinfect these FIBCs between uses in the United States. 

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Evidence collected as part of the investigation suggests that the FIBCs could be potentially contaminated in their origin country and, upon arrival in the United States, are likely being reused. If a contaminated FIBC was used to transport bulk feed or ingredients to the swine feed mill networks, a small bit of contaminated material could have been mixed into feed destined for many locations and spread the virus onto farms. 

APHIS completed follow-up testing in an attempt to provide evidence for this scenario. This follow-up testing further supports the hypothesis that PED virus could easily remain stable through the time needed to travel to the United States and infect pigs.

The first cases of novel SECD were confirmed in the U.S. in April 2013. SECD viruses quickly spread to many swine premises throughout the country, killing 7 million piglets within the first year and causing tremendous hardship for many American pork producers. APHIS, the states, and the swine industry have worked jointly to slow the spread of these diseases, including enhancing biosecurity practices.  APHIS also issued a federal order on June 5, 2014 requiring the reporting of SECD cases to assist with tracking and understanding these viruses. The number of new cases has dropped dramatically in the past year.