RSV virus fusion glycoprotein, molecular model. This is a fusion glycoprotein of human respiratory syncytial virus (RSV). This glycoprotein is used by the virus to invade host cells. Treatments for the virus have been aimed at disrupting the effect of this glycoprotein. RSV is a pneumovirus, a type of paramyxovirus. It is a major cause of respiratory tract infections in humans, and is the most common cause of bronchiolitis and pneumonia among infants.