Bird flu detected in a pig in US, raises red flags over species transmission

Sub: Sci

Sec: Health

Context:

On October 31, avian influenza A (H5N1) was confirmed in a pig on a backyard farm in Oregon, marking the first known infection of a pig by this virus in the United States.
The virus strain, clade 2.3.4.4b of influenza A / H5N1, is currently spreading globally and is known to affect various species.

Farm Conditions and Possible Transmission:

The farm housed poultry, livestock, and five pigs in close proximity, sharing water sources, housing, and equipment.
Earlier in October, 70 infected poultry on the farm were culled as a preventive measure.

CDC Concerns and Risk of Genetic Reassortment:

The CDC highlighted the adaptability of the A (H5) virus in pigs, which can be infected by influenza strains affecting humans, birds, and other animals.
The CDC warned of the potential for genetic reassortment, a process in which two or more influenza viruses infect a single host, allowing for gene-swapping and the emergence of new viruses with increased transmissibility.
Studies show that pigs have respiratory receptors similar to humans, allowing them to bind both human and avian influenza viruses, which increases the risk of transmission to humans.
The 2009 A(H1N1) pandemic is an example of a reassortment event in pigs that led to a global outbreak.

2024 Human and Animal Avian Flu Cases:

So far in 2024, 44 human cases of avian flu have been documented, with 24 linked to cattle, 19 to poultry, and one untraceable.
In the US, over a million poultry have been infected since January, with outbreaks across 48 states, impacting 10,465 wild birds and 403 dairy herds in 14 states.
Since May 2022, avian influenza has been detected in 404 mammals across 23 species, including cats, polar bears, brown bears, coyotes, and raccoons.

Avian Influenza:

A disease caused by avian influenza (AI) Type A viruses found naturally in wild birds worldwide.
AI viruses are broadly classified as low pathogenic AI (LPAI) and highly pathogenic AI (HPAI) viruses, based on their pathogenicity.
The two virus types identified so far in the outbreaks H5N1 and H5N8 come under the category of Highly Pathogenic Avian Influenza (HPAI), which is of major concern to those keeping birds, because it leads to disease and death of fowl and causes economic havoc. H5N1 is a known threat to humans as well.
The virus can infect domestic poultry including chickens, ducks, turkeys and there have been reports of H5N1 infection among pigs, cats, and even tigers in Thailand zoos.
There is no vaccine against H5N1.
Most avian influenza viruses do not infect humans, however some, such as A(H5N1) and A(H7N9), cross the species barrier and cause disease or subclinical infections in humans and other mammals as well.
The Avian (H5N1) virus subtype, a highly pathogenic virus, first infected humans in 1997 during a poultry epidemic outbreak in Hong Kong SAR, China.

Types of Influenza Virus

There are four types of influenza viruses: influenza A, B, C, and D.
Influenza A and B are the two types of influenza that cause epidemic seasonal infections nearly every year.
Avian influenza belongs to Type A viruses
Type A viruses are classified based on two proteins on their surfaces – Hemagglutinin (HA) and Neuraminidase (NA).
There are about 18 HA subtypes and 11 NA subtypes.
Several combinations of these two proteins are possible e.g., H5N1, H7N2, H9N6, H17N10, H18N11 etc.
Influenza C mainly occurs in humans, but has been known to also occur in dogs and pigs.
Influenza D is found mainly in cattle. It’s not known to infect or cause illness in humans yet.

Source: DTE