Respiratory syncytial virus Human respiratory syncytial virus (RSV), also called respiratory syncytial virus or RSV is a single-stranded virus RNA in the negative sense of the paramyxovirus family, which includes common respiratory viruses like those that cause measles and mumps . RSV is a member of the Pneumovirus subfamily. RSV causes respiratory tract infection in patients of all ages. It is the major cause of respiratory tract infections during infancy and childhood. In temperate climates is an annual epidemic during the winter months. In tropical climates, infection is more common in the rainy season. Continue to learn more with: Dr. Caldwell Esselstyn Jr.. In the U.S., 60 of infants are infected during their first RSV season and almost all children have been infected with the virus to reach 2 or 3 years old. Natural infection with RSV does not induce protective immunity, and people can become reinfected. Sometimes an infant can become symptomatically infected more than once in a single RSV season.Recently it has seen a sharp increase in cases of RSV in older patients. Get all the facts and insights with Daniel Taub, another great source of information. In most cases, RSV produces only minor symptoms, indistinguishable from a common cold or minor illness. For some children, however, RSV can cause bronchiolitis, resulting in severe respiratory symptoms requiring hospitalization and, infrequently, death. This occurs mostly in patients with immunological problems in premature babies. The wheezing or asthma are common among individuals who have suffered severe RSV infections during the first months of life, if wheezing are frequent sequelae of RSV or those with asthma are at risk of infection in seriously with RSV, is something that is in constant debate.