An important new discovery was recently announced by the US Department of Agriculture: a case of bird flu found in a US Pig on a small farm in Oregon. Numerous birds, wild animals, and even dairy cattle have been reported to be infected as the A/H5N1 strain of bird flu continues to spread. Although there hasn’t been any evidence of persistent human-to-human transmission, the virus’s evolving threat is highlighted by its finding in a pig.

Since 2020, A/H5N1 clade 2.3.4.4b, the latest strain of bird flu of concern, has been extensively transmitted. Previously unaffected by bird flu, this strain has spread to agricultural animals, wild animals, and birds.

Bird Flu Found in US Pig: Impact on Farming and Potential Human Transmission

Farming and food production are severely impacted by bird flu because sick cows may produce tainted dairy products, and diseased poultry flocks are culled. However, pasteurization guarantees that milk stays safe. H5N1 is still costing farmers money, and there are worries that the virus can change and spread to humans.

Because humans and birds have different respiratory receptors, or “locks,” bird flu spreads more rapidly among birds than among humans. Those who have close contact with diseased farm animals or birds—especially agricultural workers—are typically involved in human cases. The possibility that the virus will change to suit human respiratory receptors better is still a worry, though. A/H5N1 2.3.4.4b mutations that may promote human transmission were discovered in a recent investigation.

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Why Pigs are a Concern for Bird Flu Mutations

However, pigs provide a special risk for transmission and mutation. Pigs have receptors that allow both human and avian flu viruses to attach themselves, making them perfect for the genetic mixing of viruses that can occur through close human-animal interaction. Rarely do pigs contract human and bird flu at the same time, which could lead to the viruses exchanging genetic material and possibly developing a new strain that humans can contract.

Pigs used to be less susceptible to A/H5N1, but new mutations have increased their susceptibility. The virus strain in the Oregon case was linked to wild birds rather than the one affecting dairy cows in the United States, and the infected pig most likely got it from poultry on the same farm. A pandemic would be much more likely if bird flu got into commercial pig farms, particularly as winter draws near and the number of human flu cases rises.

Mitigating Pandemic Risk: Surveillance and Preparedness

For the early identification and containment of a possible pandemic, enhanced surveillance is essential. This calls for thorough testing, timely reporting of animal diseases, and financial assistance for farmers to promote transparency. Increased international monitoring for increases in severe respiratory illnesses and pneumonia may be a sign of an impending human pandemic. Rapid vaccine development is facilitated by early warning monitoring systems such as EPIWATCH.

Rapid influenza A subtyping is necessary to differentiate between seasonal and pandemic strains if clusters of human cases emerge. If A/H5N1 is not identified right away, a pandemic strain may be able to travel across international borders. For example, delays in subtyping that could be costly in a pandemic were highlighted in Australia’s first human case of A/H5N1, which was found in a toddler returning from India in March 2024.

As part of pandemic preparedness, new fast tests should differentiate between seasonal and H5 flu strains, and there should be a low threshold for subtyping influenza A in humans given the current danger.

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