Avian Influenza A (H5N1) Detected in Oregon Pig

November 6, 2024

A pig in Oregon tested positive for avian influenza A (H5N1). This is as it marks the virus infecting a new mammalian host. The case was linked to a farm with poultry, livestock, and pigs sharing space. The infection was confirmed on October 30 after initial reports on October 25.

Spread of H5N1

The strain involved is clade 2.3.4.4b of influenza A / H5N1. It is currently spreading globally and affecting various species. This raises concerns about a potential new pandemic.

Possible Infection Routes

The likely cause of infection in the pig was shared resources with infected poultry. Earlier in October, 70 infected birds were culled from the farm. The sharing of water, housing, and equipment created a pathway for the virus.

On November 4, the CDC expressed concerns about the adaptability of the H5 virus in pigs. Pigs can be infected by influenza viruses from humans, birds, and other animals. This adaptability increases the risk of genetic reassortment.

Genetic Reassortment Explained

Genetic reassortment occurs when multiple influenza viruses infect a single host. This can lead to the emergence of new viruses with different properties. Such viruses may spread more easily among animals or humans.

Pigs as Hosts

Pigs share similar receptors in their respiratory tracts with humans. This allows them to bind both human and avian influenza viruses. A study published in 2010 brought into light this similarity, increasing the risk of transmission between species.

Past reassortment events in pigs have led to outbreaks. The 2009 A(H1N1) pandemic is one notable example. The CDC warns that while the risk exists, it remains low for the general public.

Current Human Cases

In 2024, there have been 44 reported human cases of avian flu. Of these, 24 are linked to cattle and 19 to poultry. One case remains untraceable.

Since January 2024, over a million poultry have been affected by avian flu in the US. Outbreaks have been reported in 48 states. Additionally, 10,465 wild birds have tested positive for the virus.

Mammalian Infections

Since May 2022, avian influenza has been detected in 404 mammals across 23 species. Affected species include cats, polar bears, brown bears, coyotes, and raccoons. This marks the virus’s expanding host range.

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