Human respiratory syncytial virus (RSV) is a negative sense, single-stranded RNA virus of the family Paramyxoviridae, which includes common respiratory viruses such as those causing measles and mumps. RSV is a member of the paramyxovirus subfamily Pneumovirinae.
RSV causes respiratory tract infections in patients of all ages. It is the major cause of lower respiratory tract infection during infancy and childhood. In temperate climates there is an annual epidemic during the winter months. In tropical climates, infection is most common during the rainy season. In the United States, 60% of infants are infected during their first RSV season, and nearly all children will have been infected with the virus by 2-3 years of age. Natural infection with RSV does not induce protective immunity, and thus people can be infected multiple times. Sometimes an infant can become symptomatically infected more than once even within a single RSV season. More recently, severe RSV infections have increasingly been found among elderly patients as well.
For most people, RSV produces only mild symptoms, often indistinguishable from common colds and minor illnesses. For some children, however, RSV can cause bronchiolitis, leading to severe respiratory illness requiring hospitalization and, rarely, causing death. This is more likely to occur in patients that are immunocompromised or infants born prematurely.
Recurrent wheezing and asthma are more common among individuals who suffered severe RSV infection during the first few months of life than among controls; whether RSV infection sets up a process that leads to recurrent wheezing or whether those already predisposed to asthma are more likely to become severely ill with RSV is a matter of considerable debate.
Prevention
As the virus is ubiquitous in all parts of the world, avoidance of infection is not possible. Epidemiologically, a vaccine would be the best answer. Unfortunately, vaccine development has been fraught with spectacular failure and with difficult obstacles. Researchers are working on a live, attenuated vaccine, but at present no vaccine exists. However, a moderately effective prophylactic drug is available for infants at high risk. This drug is a monoclonal antibody directed against RSV proteins. It is given by monthly injections, which are begun just prior to the RSV season and are usually continued for five months.
Treatment
At present, treatment of RSV infection consists of supportive care, including hydration and oxygenation, until the disease can run its course. Ribavirin, a broad-spectrum antiviral agent, was once employed as adjunctive therapy for the sickest patients; however, its efficacy has been called into question by multiple studies, and most institutions no longer use it, even when the patient is in dire straits.
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