Bird flu: UK is seeing its largest-ever outbreak

In the UK, more than 150 cases of bird flu have been reported between September and November.

This outbreak has led to the death of nearly 100 million poultry birds around the world.
It is threatening wild bird populations in Europe and the US.
Threat: 15 species of seabirds have tested positive for HPAI for the first time.
Deaths have been reported in species like great skuas, which are worrying due to their magnitude and potential to threaten the species’ persistence in the UK.

Avian influenza is a highly contagious viral disease that occurs primarily in poultry and wild water birds.
Avian influenza viruses are either high or low-pathogenic viruses (HPAI and LPAI, respectively).
The variant depends on the molecular characterization of the virus and its ability to cause disease and mortality in chickens.
- These mutate rapidly and can combine genetic material from other influenza viruses into their genomes to produce new variants.
The bird flu spreads through their droppings, contaminating the water bodies they visit.
Avian influenza can be transmitted from animals to humans in two main ways:
- Directly from birds or from contaminated environments.
- Through an intermediate host, such as a pig.

Western Europe’s avian flu season starts in the autumn.
It is when millions of migratory birds from colder climates such as geese, ducks, and swans arrive for the winter.
Their contact with the domestic poultry population may result in the spread of any pathogens carried by them.

There are four types of influenza (flu) viruses: A, B, C, and D.
Wild aquatic birds, including gulls, terns, shorebirds, and wild waterfowl, such as ducks, geese, and swans are considered reservoirs (hosts) for avian influenza A viruses.
Subtypes of Influenza A Viruses:
- Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: hemagglutinin (HA) and neuraminidase (NA).
- There are 18 known HA subtypes and 11 known NA subtypes.
- All known subtypes of influenza A viruses can infect birds, except subtypes A(H17N10) and A(H18N11).

Avian influenza A viruses are classified into the following two categories:
- low pathogenicity avian influenza (LPAI) A viruses: Low pathogenic avian influenza viruses cause either no signs of disease or mild disease in chickens/poultry (such as ruffled feathers and a drop in egg production).
- highly pathogenic avian influenza (HPAI) A viruses: Highly pathogenic?avian influenza viruses?cause severe disease and high mortality in infected?poultry.?
Both HPAI and LPAI viruses can spread rapidly through poultry flocks.
Both LPAI and HPAI A viruses have caused mild to severe illness in infected humans.