Respiratory syncytial virus

A virus species belonging to the Paramyxoviridae, a globally distributed, single-stranded (ss), unsegmented RNA virus from the Paramyxoviridae family (genus Pneumoviridae - Pneumoviruses). The virus has a bilayer lipid envelope in which glycoproteins are embedded, including a fusion (F) and an adhesion (G) protein. Two groups of RSV are distinguished: A and B, which differ in the antigenic structure of the G protein. Strains of both groups circulate simultaneously, but RSV A predominates in most years.

The virus infects the cilia-bearing epithelial cells of the upper respiratory tract. This is where viral replication takes place. The formation of syncytia caused by the F protein and the onset of inflammation cause reversible damage to the epithelia. The necrosis of such syncytia as well as the inflammatory exudates lead to an obstruction of the airways. The infection is typically self-limiting. The epithelia regenerate within 4-8 weeks.

RSV is a pathogen of acute diseases of the upper and lower respiratory tract. RSV leads to clinical outbreaks every year with a certain seasonal frequency (late autumn and winter). In the remaining months sporadic infections occur. The virus is highly contagious. More than 50% of children <1 year are exposed. Newborns and young infants are protected from RSV-related disease in the first 4-6 weeks of life by diaplacentally transmitted antibodies. Premature infants can also become severely ill with RSV infection in the first weeks of life due to a reduced supply of maternal antibodies.

In older infants and toddlers, RSV infection is the most common cause of diseases of the lower respiratory tract and associated hospital admissions. Within the 1st year of life 50-70% and until the end of the 2nd year of life almost all children have undergone at least one infection with RSV.

Humans are the only relevant reservoir for human RSV. Transmission occurs primarily by droplet infection from an infectious person to a contact person. Conjunctiva and nasal mucous membranes form the entry portal. It is assumed that transmission is also possible indirectly via contaminated hands, objects and surfaces. RSV can survive in respiratory secretions for 20 minutes on hands, 45 minutes on paper towels and cotton gowns and up to several hours on disposable gloves, stethoscopes and plastic surfaces. Adolescents and adults play a role as asymptomatic or low symptom carriers. Children who are passively immunized against RSV can also be temporary carriers of RSV, as the antibodies do not prevent infection of the upper airways. Medical staff and other contacts of the patients can thus contribute to a rapid, even nosocomial spread, if protective and hygienic measures are inadequate.

There is no long-term immunity. Reinfections are frequent, especially in adults with regular contact to small children.

98% of infections in infants occur in the nasopharynx as harmless rhinitis. Severe forms with bronchiolitis and pneumonia are possible. Otitis media is a frequent complication.

The pathogen should be detected promptly in order to effectively prevent nosocomial RSV infections and to make therapeutic decisions. As for other viral pathogens of respiratory diseases, nasopharyngeal secretion from nasopharyngeal rinsing water, aspiration or swabs is suitable for the detection of RSV.

PCR: Genome detection by PCR is very specific, fast and highly sensitive, even with low viral load in the sample.

For antigen detection, rapid tests based on enzyme immunoassays (EIA) are usually available, which give a result within 20-75 minutes. They are evaluated for persons up to 18 years of age. The sensitivity of EIA is in the range of 50-90% and their specificity is 75-100%, with the positive predictive value depending strongly on the age of the patients and the season.

Furthermore, detection methods based on immunofluorescence techniques (IFT) can be used, which achieve a sensitivity and specificity of over 90%.

Virus culture is possible (formerly gold standard in laboratory diagnostics). It requires specialized personnel and is time-consuming, since cytopathic effects only occur after 4-7 days, and cannot be performed in every laboratory. Due to the spread of antigen and genome detection with high sensitivity, it has become less important in recent years.

Antibody detection is of secondary importance compared to direct pathogen detection. In the case of an RSV infection, antibodies are only formed in low concentrations. In order to detect an increase in titer, two sera must be tested at least 2-4 weeks apart. Antibody detection is therefore particularly suitable for retrospective confirmation of the diagnosis and for surveillance and research purposes.

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