Ziresovir is primarily used in the treatment of respiratory syncytial virus (RSV) infections, particularly in pediatric and immunocompromised patients. It functions as a fusion inhibitor, preventing the virus from entering host cells and thereby reducing the severity and duration of the infection. Clinical trials have shown its efficacy in lowering viral load and improving respiratory symptoms, making it a promising therapeutic option for managing RSV-related illnesses. Additionally, it is being explored for potential use in preventing RSV infections in high-risk populations.