Bird flu: should we be concerned?

First detected in chickens in Scotland in 1959, H5N1–avian influenza, or bird flu – is a type of avian influenza A virus that causes a highly infectious and severe respiratory disease in birds (Mahase, 2023a). According to the US Centers for Disease Control and Prevention (CDC, 2022), influenza A viruses are divided into subtypes based on two glycoproteins on the surface of the virus: hemagglutinin (H) and neuraminidase (N). There are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes, which can be further broken down into different genetic ‘clades’ based on the similarity of their gene sequences.

Highly pathogenic avian influenza (HPAI) type A (H5N1) infections during the 2021–2022 epidemiological year have been the largest in European history, involving 37 countries; 2520 HPAI outbreaks in poultry resulting in 50 million dead or culled birds in affected establishments; 227 detections in captive birds; and 3867 detections in wild birds (Adlhock et al, 2023). Further, the high infection pressure due to the continuous circulation of H5N1 ‘in the wild reservoir has led to frequent introductions of the virus into poultry populations across Europe’ (Adlhock et al, 2023).