False-colour transmission electron micrograph (TEM) of virions, or virus particles, of the respiratory syncytial virus. RS virus, as it is also known, is a member of the paramyxovirus group which is a major cause of human respiratory tract infections in temperate climates, particularly during the winter months. In adults the virus only affects the upper respiratory tract, but infants may be more severely affected & may develop bronchiolitis - inflammation of the bronchioles - or potentially fatal bronchopneumonia. Magnificat- ion: x40,000 at 35mm size. Virus red/pink on blue background.