Bird flu viruses, beyond the well-known H5N1 strain, are increasingly raising concerns among scientists due to their potential to mutate and spread more effectively among humans. Researchers are particularly focused on the H9N2 virus, a subtype that, while causing mild symptoms in poultry, can lead to more severe illness in people, especially children.

A study published in November by researchers in Hong Kong revealed that H9N2 has acquired mutations over the past decade that enhance its ability to spread among humans and cause more severe disease. While there have been fewer than 200 reported cases of H9N2 in humans since 1998, the number has been rising, with China reporting 29 human cases last year, compared with 11 in 2024.

Dr. Kelvin To, a clinical microbiologist who led the November study, believes that these numbers are likely underestimates. He explained that many infected individuals are never tested, allowing the virus to spread undetected. This highlights a critical challenge in tracking and containing the virus.

The rise of H9N2 and its evolving characteristics underscore the broader threat posed by avian influenza viruses. These viruses, which primarily infect birds, can sometimes jump to other species, including humans. The process of a virus adapting to a new host often involves mutations that allow it to bind more effectively to cells in the new host's respiratory system.

Scientists use AI and machine learning to analyze the genetic sequences of these viruses, predict potential mutations, and assess the risk of human transmission. These AI models can identify patterns in viral evolution that might be missed by traditional methods, providing early warnings about emerging threats. The implications for society are significant, as the emergence of a highly transmissible and virulent avian influenza virus could lead to a pandemic, similar to the 1918 Spanish flu or the more recent COVID-19 pandemic.

Current efforts are focused on improving surveillance of avian influenza viruses in both poultry and wild birds, as well as developing more effective vaccines and antiviral treatments. International collaborations are also crucial for sharing data and coordinating responses to outbreaks. The World Health Organization (WHO) plays a key role in monitoring the global spread of avian influenza and providing guidance to countries on how to prepare for and respond to potential outbreaks.