Update: Respiratory Syncytial Virus Activity -- United States, 1997-98 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 among infants and young children in the United States (1). Outbreaks occur annually throughout the country (2,3). 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 reported by NREVSS for July 1992-June 1997 and presents provisional surveillance results for July-November 1997. These data indicate onset of widespread RSV activity for the 1997-98 season.

Since July 1992, a total of 100 clinical and public health laboratories in 47 states have participated in 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. RSV activity is considered by NREVSS to have become widespread during the first of 2 consecutive weeks during which at least half of participating laboratories report any RSV detections. This definition generally indicates a mean percentage of specimens positive by antigen detection in excess of 10%.

From July 1992 through June 1997, onset of widespread RSV activity began each November and continued for a mean of 22 weeks, until April or mid-May (Figure_1). In most parts of the 48 contiguous states, the peak in activity occurred each year in January or February; however, in the Southeast, activity peaked as early as November or December (3). For the reporting period beginning July 1997, a total of 71 laboratories in 41 states reported results of testing for RSV. Since the week ending November 7, more than half of the participating laboratories reported detections of RSV each week, indicating onset of widespread RSV activity for the 1997-98 season.

Reported by: National Respiratory and Enteric Virus Surveillance System collaborating laboratories. Respiratory and Enteric Viruses 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 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 who have underlying cardiac or pulmonary disease or are immunocompromised are at risk for serious complications from this infection. Because natural infection with RSV provides limited protective immunity, RSV can cause repeated symptomatic infections throughout life. In adults, RSV usually causes upper respiratory tract symptoms but can cause lower respiratory tract disease, especially in 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 (7). Sources for nosocomially acquired infection include infected patients, staff, or 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); RSV immune globulin intravenous (human) is available for prevention of serious RSV infections in some high-risk infants and children (9). Vaccines for RSV are being developed, but none have been demonstrated to be safe and efficacious in infants (10).

References

1. Institute of Medicine. Appendix N: prospects for immunizing against respiratory syncytial virus. In: New vaccine development: establishing priorities -- Volume 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}. Presented at: 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. Mlinaric-Galinovic G, Falsey AR, Walsh EE. Respiratory syncytial virus infection in the elderly. Eur J Clin Microbiol Infect Dis 1996;15:777-81.

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. Resp 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. Committee on Infectious Diseases, Committee on Fetus and Newborn, American Academy of Pediatrics. Respiratory syncytial virus immune globulin intravenous: indications for use. Pediatrics 1997;99:645-50.

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 Research 1994;32:13-36.

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