H5N1 is a subtype of the influenza virus that primarily affects birds but can also infect humans and other animals. It is known for causing severe respiratory illness and has a high mortality rate in humans. The virus is often found in domestic poultry, such as chickens and ducks, and can spread to humans through direct contact with infected birds or contaminated environments. Since its emergence in the late 1990s, H5N1 has raised concerns about potential outbreaks and pandemics. Health organizations, including the World Health Organization (WHO), monitor its spread and work on prevention strategies to protect both animal and human health.