Respiratory Syncytial Virus (RSV) is the major cause of respiratory illnesses in all ages. Ti represents the most frequent cause of serious respiratory tract infections in infants and children younger than 4 years of age but is also responsible for severe problems in elderly and immunocompromised patients giving rise to high death rates. Pneumonia and bronchiolitis are the two most frequent severe infections prevalent in infants aged 2 to 6 months. Infection of older children and adult may be mild, usually self-limiting, causing nasal stuffiness and discharge not distinguishable from a common cold. Each year, up to 50% of infants are infected. RSV disease causes about 70% of bronchiolitis and results in 80,000 to 125,000 hospitalisations in the US each year. Those children who require hospitalisation are newborns and those who suffer from asthma, lung disorders or heart problems. Moreover, RSV bronchiolitis in the first year of life is one of the most important risk factors for the subsequent development of asthma.It is a highly contagious disease through contact with respiratory secretions. It is also a common cause of nosocomial infections whose prevalence increases during community outbreaks through casual contacts.
