Avian influenza

Avian Influenza: A Bird’s Eye View of a Deadly Virus

Imagine a world where a simple bird flu could turn into an epidemic, threatening not just the avian population but also humans and other mammals. That’s exactly what Avian Influenza (AI) is—a virus that can jump from birds to people under certain conditions. This viral threat has been around for decades, with its first known outbreak in Scotland back in 1959, but it continues to evolve and pose new challenges.

Understanding the Virus

Avian influenza, caused by the Influenza A virus, primarily affects birds. However, this virus is not just limited to its avian hosts; it can also infect mammals, including humans. The symptoms of AI vary widely depending on the strain and species affected. For instance, low pathogenic avian influenza (LPAI) might cause only mild or no symptoms in chickens, while high pathogenic avian influenza (HPAI) can lead to severe breathing difficulties and even death.

Classification and Reporting

The classification of virus strains is based on their effect on domestic chickens. The World Organization for Animal Health requires the reporting of LPAI H5 and H7 detections because these subtypes have a potential to mutate into highly pathogenic strains, which can be devastating for poultry populations.

The Viral Genome

Influenza A is an RNA virus with a complex genome. It has 11 viral genes and two proteins on its surface: hemagglutinin (H) and neuraminidase (N). These antigens are crucial as they are targeted by neutralizing antibodies, which can change during epidemics or epizootics. There are 18 types of H and 11 types of N found in influenza A viruses, with H1-H16 being present in birds and N1-N11 in humans.

Subtypes and Transmission

Subtypes of the virus are defined by the combination of H and N proteins. Almost all possible combinations have been isolated from wild birds, but further variations can lead to significant differences in the virus’s ability to infect and cause disease. The Influenza virus nomenclature provides a detailed description of specific isolates, including the species it was isolated from, place and year of collection, laboratory reference number, and type numbers for hemagglutinin and neuraminidase proteins.

Transmission and Spread

Avian influenza is spread through saliva, mucus, and feces. Infected birds can transmit the virus to other birds or even humans if they are in close contact. The virus can survive for long periods in water and at low temperatures, making it a persistent threat.

Human Infections

Humans can become infected with avian flu after prolonged close contact with infected birds. However, there is no sustained transmission from one person to another. Factors such as binding specificity for sialic acid receptors and genetic mutations play a crucial role in preventing epidemics in humans or other mammals.

Global Impact

The impact of avian influenza extends beyond just the bird population. Between 1959 and 1995, there were 15 outbreaks of highly pathogenic avian influenza (HPAI) in poultry, resulting in varying losses. Since then, several virus strains have become endemic among wild birds, leading to increasingly frequent outbreaks among domestic poultry.

Outbreaks and Control

The first known outbreak occurred in Scotland in 1959, with subsequent global outbreaks causing significant concern. The HPAI strain H5N1 has been particularly deadly, with the World Health Organization recording 948 cases leading to 464 deaths between 2003 and November 2024.

The virus has also affected other animals, including cats, dogs, ferrets, pigs, and birds. Poultry surveillance is routine in many countries, while dairy cows have recently been infected, showing the virus can persist on equipment and spread through cow-to-cow contact.

Global Efforts

A global partnership was formed in 2005 to address avian flu, with new networks for detection and response emerging. The World Health Organization recognizes the need for more transparent sharing of vaccines and benefits. Cooperative measures in response to HPAI have served as a basis for programs related to other emerging infectious diseases.

Conclusion

Avian influenza remains a significant threat to both avian populations and humans, with its ability to mutate and spread making it a persistent challenge. The virus’s complex nature and the global efforts required to control it highlight the importance of ongoing research, surveillance, and international cooperation in addressing this deadly disease.

By understanding the intricacies of Avian Influenza, we can better prepare for potential outbreaks and mitigate their impact on both animal and human health.