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Respiratory Syncytial Virus (RSV)

Respiratory syncytial virus (RSV) is a common cause of winter outbreaks of acute respiratory disease, and results in an estimated 90, 000 hospitalizations and 4500 deaths each year from lower respiratory tract disease in both infants and young children in the United States. According to the National Respiratory and Enteric Virus Surveillance System, RSV season generally begins in November and continues for a mean of 22 weeks, through April. Most severe manifestations of infection with RSV occur in infants aged 2-6 months; however, children of any age with underlying cardiac or pulmonary disease or who are immunocompromised are at risk for serious complications from this infection. Because natural infection with RSV provides limited protective immunity, RSV causes repeated symptomatic infections throughout life. In adults, RSV usually causes upper respiratory tract manifestations but may cause lower respiratory tract disease--especially in the elderly and in immunocompromised persons. Infection in immunocompromised persons can be associated with high death rates. RSV is a common, but preventable, cause of nosocomially acquired infection; the risk for nosocomial transmission increases during community outbreaks. Sources for nosocomially acquired infection include infected patients, staff, visitors, or contaminated surfaces. Ribavirin therapy may be considered for patients who are seriously ill or who are at high risk for severe complications of the infection. In addition, RSV immune globulin was licensed for use in January 1996. Vaccines for RSV are being developed, but none have been demonstrated to be safe and efficacious.

Conventional viral culture or rapid antigen testing can detect RSV. Cultures require 3 to 14 days’ incubation before cytopathic effects are seen. The sensitivity of cultures is often impaired by the lability of the virus during specimen transport to the laboratory. Rapid antigen testing for RSV overcomes this limitation and is much quicker to perform. Comparisons with culture have shown the rapid antigen test to be very sensitive and specific. RSV antigen results are reported as negative or positive. Reference value is a negative result.

Adequate specimen collection is crucial to achieve accurate test results. A nasopharyngeal aspirate should be obtained by the following method:

1.With patient in a supine position, squeeze approximately 1cc normal saline in each nostril.

2.Pass the tip of a Delee mucus trap into the nostril while applying suction (preferably by means of a wall suction pump). Using a rotating motion, slowly withdraw the catheter.

3.Repeat the procedure with the second nostril for an optimal combined sample.

4.Wash out the tubing with saline into the mucus trap to remove any residual specimen. Remove the top of the mucus trap and place lid (located at bottom of trap) on trap.

5.Place specimen on ice and transport to lab immediately for testing. Do not place in viral transport media.

Nasal swabs are not adequate for RSV testing and may cause false negative results. An equivocal or negative test does not eliminate the possibility of RSV infection, because inadequate collection, improper handling, or low level virus shedding may cause them.

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