Avian Leukosis Virus (ALV) is a retrovirus that primarily affects birds, particularly domestic chickens. It can lead to various health issues, including tumors and immunosuppression. ALV is transmitted through direct contact or contaminated environments, making it a concern for poultry farmers. There are several subtypes of ALV, each associated with different diseases. Infected birds may show no symptoms initially, but over time, they can develop conditions like lymphoid leukosis or myeloid leukosis. Vaccination and biosecurity measures are essential for controlling the spread of this virus in poultry populations.