Dive Brief:
- The United States has detected its first case of H5N1 bird flu in a pig, a worrying sign for scientists who have warned the virus' movement to swine could be a bellwether for a potential pandemic.
- The case was identified in a backyard farm in Oregon that had a mix of poultry and livestock, including swine. All pigs at the farm were euthanized, with the U.S. Department of Agriculture noting the animals were never intended to enter the food supply.
- The risk to public health is still low, according to the USDA and the Centers for Disease Control and Prevention. However, Katelyn Jetelina, an epidemiologist and CDC consultant, told Agriculture Dive that “these moves the virus is making is making public health very uncomfortable.”
Dive Insight:
Pigs are known as mixing vessels for flu viruses because they can harbor both human and zoonotic influenza viruses at the same time, increasing the threat of a new virus that can more easily infect people.
“If a pig is infected with human and bird flu strains, then the virus can switch genes,” Jetelina said. “And when this happens, the virus could become more adaptable to human spread and then become a pandemic.”
Pigs were the source of the 2009 H1N1 pandemic, Jetelina said, and the recent detection in Oregon raises alarms for public health officials.
The backyard farm housed a mixture of livestock and poultry that shared water, shelter and equipment, according to the U.S. Department of Agriculture. This combination has resulted in the transmission of bird flu between species in other states.
Unlike other animals on the premises, the swine showed no flu-like symptoms. Local and federal officials tested five pigs for the virus and confirmed at least one positive detection on Wednesday. Test results were negative for two of the pigs, and results are pending for two more.
The USDA’s National Veterinary Services Laboratory has conducted genomic sequencing from infected poultry on the farm, and has not identified any changes to the H5N1 virus, according to the department, suggesting no evidence of a virus more transmissible to people.
At least 39 people have tested positive for bird flu as a result of a current outbreak affecting poultry and dairy cattle, according to the CDC. Most of the cases have affected farmworkers with direct access to sick animals, although one person in Missouri contracted the virus from an unknown source.
An investigation into the Oregon farm is underway as questions remain about how the virus spread to pigs. While the development is worrisome, Jetelina said the risk for further transmission is lower if federal officials determine this was an isolated case.
"If it's isolated, it's not very meaningful," Jetelina said. "But we do want to get a better handle on this virus, because we don't want to give it any more opportunities to swap genes, especially now that we're going into flu season.”
