Avian Influenza

Excerpt

Avian influenza, commonly known as "bird flu," is a zoonotic disease caused by avian influenza A viruses. While these viruses primarily infect birds, they can occasionally transmit to humans, resulting in severe illness and potentially death. This disease has garnered significant global attention due to its potential to cause widespread, lethal outbreaks in poultry and severe infections in humans. Highly pathogenic strains are particularly concerning due to their ability to mutate rapidly and spread efficiently, thereby posing serious threats to public health and economic stability. As a result, healthcare providers must maintain high suspicion when identifying and managing cases to prevent rapid disease progression and severe outcomes.Influenza A viruses, part of the Orthomyxoviridae family, are classified into subtypes based on 2 distinct surface glycoproteins—hemagglutinin (H), which has 16 known antigenic variations, and neuraminidase (N), with 9 variations. These subtypes are commonly identified by combinations such as H5N1 or H7N9. The Orthomyxoviridae family also includes influenza B and C viruses, thogotovirus, and isavirus. While influenza B and C viruses can infect certain other species, only influenza A viruses are known to infect birds.

Most human infections occur through contact with infected domestic poultry, either via secretions or contaminated environments. Wild aquatic birds, however, serve as the natural reservoir for these viruses. Human-to-human transmission is rare, but documented cases highlight the pandemic potential of these viruses if they acquire enhanced transmissibility.

Although the exact modes of transmission between birds are not fully understood, the oral-fecal route is widely considered the primary method of transmission. Avian influenza viruses in birds are categorized into 2 categories—highly pathogenic avian influenza (HPAI) viruses and low pathogenicity avian influenza (LPAI). LPAI viruses are more common and typically cause minimal illness in birds, while HPAI strains are associated with severe systemic illness.

In humans, both HPAI and LPAI strains can trigger significant outbreaks, with HPAI often resulting in more severe cases. Notable examples include the H5N1 outbreak in Hong Kong in 1997 and the H7N9 outbreak in China in 2013, both characterized by high case fatality rates. These events underscore the importance of surveillance, early diagnosis, and timely intervention to prevent widespread transmission of the disease. As new highly pathogenic strains of avian influenza continue to emerge across various regions, reflecting the growing genetic diversity of circulating viruses, ongoing research is essential to mitigate potential threats.

Due to the disease's potential severity in humans, healthcare professionals must remain vigilant when assessing patients with relevant exposure history and symptoms. Early recognition, timely laboratory confirmation, and appropriate management are critical for improving outcomes and reducing the risk of further transmission.