Update: Respiratory Syncytial Virus Activity -- United States, 1996-97 Season

Respiratory syncytial virus (RSV), a common cause of winter outbreaks of acute respiratory disease, 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 (1). Outbreaks occur annually throughout the country (2). RSV activity in the United States is monitored by the National Respiratory and Enteric Virus Surveillance System (NREVSS), a voluntary, laboratory-based system. This report summarizes trends in RSV from the NREVSS from July 1, 1990, through June 28, 1996, and presents provisional surveillance results for June 29-November 29, 1996. These data indicate onset of widespread RSV activity for the 1996-97 season.

Since July 1, 1990, a total of 98 hospital-based and public health laboratories in 47 states have participated in the NREVSS and have reported weekly to CDC the number of specimens tested for RSV by the antigen-detection and virus-isolation methods and the number of positive results. Widespread RSV activity is defined by the NREVSS as the first of two consecutive weeks during which at least half of the participating laboratories report any RSV detections. This definition generally indicates a mean percentage of specimens positive by antigen detection in excess of 10%.

During the previous six seasons, from July 1990 through June 1996, onset of widespread RSV activity began in November and continued for a mean of 22 weeks until April (Figure_1). In most parts of the 48 contiguous states, activity peaked each year in January or February; however, in the Southeast, activity peaked as early as November or December (3). For the reporting period June 29-November 29, 1996, a total of 75 laboratories in 45 states reported results of testing for RSV. Since the week ending November 22, more than half of the participating laboratories reported detections of RSV on a weekly basis, indicating onset of widespread RSV activity for the 1996-97 season.

Reported by: National Respiratory and Enteric Virus Surveillance System collaborating laboratories. Respiratory and Enterovirus Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: During the RSV season, health-care providers should consider the role of RSV as a cause of acute respiratory disease in both children and adults. Most severe manifestations of infection with RSV (e.g., pneumonia and bronchiolitis) 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 (4-6). Infection in immunocompromised persons can be associated with high death rates (6).

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 fomites. Nosocomial outbreaks or transmission of RSV can be controlled with strict attention to contact-isolation procedures (7). In addition, chemotherapy with ribavirin may be considered for some patients (e.g., those at high risk for severe complications or who are seriously ill with this infection) (8); respiratory syncytial virus immune globulin intravenous (human) for high-risk patients was licensed for use in January 1996 (9). Vaccines for RSV are being developed, but none have been demonstrated to be safe and efficacious (10).

References

1. Institute of Medicine. Appendix N: prospects for immunizing against respiratory syncytial virus. In: Institute of Medicine. New vaccine development: establishing priorities. Vol 1: diseases of importance in the United States. Washington, DC: National Academy Press, 1985:397-409.

2. Gilchrist S, Torok TJ, Gary HE Jr, Alexander JP, Anderson LJ. National surveillance for respiratory syncytial virus, United States, 1985-1990. J Infect Dis 1994;170:986-90.

3. Torok TJ, Clarke MJ, Holman RC, Anderson LJ. Temporal and spatial trends in respiratory syncytial virus activity in the United States, 1990-1996 {Abstract}. In: RSV after 40 years: an anniversary symposium (Charleston, South Carolina, November 9-12, 1996).

4. Dowell SF, Anderson LJ, Gary HE Jr, et al. Respiratory syncytial virus is an important cause of community-acquired lower respiratory infection among hospitalized adults. J Infect Dis 1996;174:456-62.

5. Falsey AR, Cunningham CK, Barker WH, et al. Respiratory syncytial virus and influenza A infections in the hospitalized elderly. J Infect Dis 1995;172:389-94.

6. Whimbey E, Couch RB, Englund JA, et al. Respiratory syncytial virus pneumonia in hospitalized adult patients with leukemia. Clin Infect Dis 1995;21:376-9.

7. CDC. Guideline for prevention of nosocomial pneumonia. Respir Care 1994;39:1191-236.

8. Committee on Infectious Diseases, American Academy of Pediatrics. Reassessment of the indications for ribavirin therapy in respiratory syncytial virus infections. Pediatrics 1996;97: 137-40.

9. Groothuis JR, Simoes EA, Levin MJ, et al. Prophylactic administration of respiratory syncytial virus immune globulin to high-risk infants and young children. N Engl J Med 1993;329:1524-30.

10. Murphy BR, Hall SL, Kulkarni AB, et al. An update on approaches to the development of respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV3) vaccines. Virus Res 1994;32:13-36.

    
    
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