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Epidemiologic Notes and Reports Respiratory Syncytial Virus -- Oklahoma

From November 1985 through the end of January 1986, an unusually large number of respiratory illnesses due to respiratory syncytial virus (RSV) occurred in Oklahoma.

Oklahoma Children's Memorial Hospital (OCMH), a 239-bed teaching hospital, serves Oklahoma City and is a tertiary referral center for central and western Oklahoma. From November 1985 through January 1986, more bronchiolitis was diagnosed each month among patients visiting the OCMH emergency room (ER) than in any month of the previous two winters (Figure 2). While the median age of patients during this 3-month epidemic season (5 months, range 18 days to 70 months) was similar to that seen in the previous 2 years, the sex distribution (51% female) differed in that the usual predominance of males (59% for the November 1984-March 1985 season, 67% for the January 1984-March 1984 season) was not seen. In December, the peak month of the outbreak, more than twice as many patients were hospitalized for bronchiolitis than in any month during the previous 5 years.

RSV was identified in 66 (53.2%) of 124 nasopharyngeal aspirates submitted from hospitalized patients in December for viral culture or fluorescent antibody tests. This was the largest number of positive tests and the highest rate of RSV positivity for any month since the virology laboratory began testing for RSV in 1981. For patients hospitalized at OCMH for bronchiolitis through December 10 of this epidemic period, 39 (84.8%) of 46 of those who submitted nasopharyngeal aspirates for testing had RSV infection. Twenty-five (67.6%) of 37 patients with pneumonia had RSV infection. Although the number of patients seen with RSV-related illness increased, indicators of the severity were similar to those seen in previous years. For example, of 238 patients seen in the OCMH ER for bronchiolitis from November 1, 1985, through January 31, 1986, 57 (23.9%) were admitted to the hospital, compared with 36 (16.7%) of 215 and 37 (24.2%) of 153 for the two previous seasons, respectively. Likewise, the rate of admission to the intensive-care unit for patients with laboratory-confirmed RSV illnesses was 8.8/100 ER visits for bronchiolitis, compared with 8.4/100 for the previous season (November 1984-March 1985). Two deaths at OCMH were attributed to RSV during this season; one such death occurred during the previous year.

Reports of increased rates of bronchiolitis from physicians and hospitals in areas of Oklahoma relative to previous years indicate that the RSV epidemic is not limited to Oklahoma City. Reported by W Pryor, MD, M Marks, MD, P Rettig, MD, J Waner, PhD, J Steumky, MD, D Conrad, MD, J Christensen, MD, W Chapman, MD, S Bullard, MD, J Hayes, MD, P Hines, MD, M Rock, MD, H Shalaby, PhD, S Todd, N Whitehurst, L Wall, Oklahoma Children's Memorial Hospital, Oklahoma City, C Wood, J Dudly, Immunization Div, G Istre, MD, State Epidemiologist, Oklahoma State Dept of Health; Div of Field Svcs, Epidemiology Program Office, Respiratory and Enterovirus Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: RSV infection, the most common cause of bronchiolitis among infants, occurs in seasonal epidemics that usually peak in the winter months. For the last 10 years, data from seven to 16 U.S. university virus laboratories show the average initial outbreak month (the first month with 8% or more of the year's total isolates) has been December or January; the peak outbreak month, January or February; and the duration of the outbreak, 2-4 months. Several studies have shown that the number of RSV-associated illnesses varies from year to year (1,2). The Oklahoma outbreak, plus reports from other (university) laboratories, suggest that the number of RSV-associated illnesses has increased in several locations this year. Data from these laboratories also suggest RSV activity occurred earlier than usual this season, with the average initial outbreak month being November rather than December. The number of RSV isolates reported has increased through January in all reporting regions except the South Atlantic, where the number of RSV isolates peaked in December.

RSV is the major cause of acute, lower respiratory illness among infants and young children worldwide. It is estimated that nearly 50% of children under 1 year of age are infected with RSV during an epidemic, and between one in 50 and one in 200 of these are hospitalized (3). Among children hospitalized with RSV, mortality rates between 0.5% and 5.6% have been reported (4-7), consistent with the two of 57 (3.5%) reported in this outbreak. Of particular concern during RSV outbreaks is the potential for nosocomial spread to infants and children at greatest risk for severe disease, such as those with compromised cardiac, pulmonary, or immune systems. A mortality rate as high as 37% has been reported among hospitalized children with cardiac abnormalities who became infected with RSV (7). Nosocomial RSV has also been associated with nearly a twofold increase in the duration of hospitalization (8).

Recommendations for the control of RSV spread in hospitals include strict attention to good hand-washing practices and the use of gowns when contact with respiratory secretions of RSV-infected patients is likely. RSV-infected patients should be in private rooms or cohorted with other patients likely to be infected with RSV (9,10).

References

  1. Glezen WP, Denny FW. Epidemiology of acute lower respiratory disease in children. N Engl J Med 1973;288:498-505.

  2. Kim HW, Arrobio JO, Brandt CD, et al. Epidemiology of respiratory syncytial virus infection in Washington, D.C. I. Importance of the virus in different respiratory tract disease syndromes and temporal distribution of infection. Am J Epidemiol 1973;98:216-25.

  3. Hall CB. Respiratory syncytial virus. In: Feigin RD, Cherry JD, eds. Textbook of pediatric infectious diseases. Vol. II. Philadelphia: WB Saunders, 1981;1247-67.

  4. Eriksson M, Forsgren M, Sjoberg S, von Sydow M, Wolontis S. Respiratory syncytial virus infection in young hospitalized children. Identification of risk patients and prevention of nosocomial spread by rapid diagnosis. Acta Pediatr Scand 1983;72:47-51.

  5. Clarke SKR, Gardner PS, Poole PM, Simpson H, Tobin JO. Respiratory syncytial virus infection: admissions to hospital in industrial, urban, and rural areas. Report to the Medical Research Council Subcommittee on Respiratory Syncytial Virus Vaccines. Br Med J 1978;2:796-8.

  6. Gardner PS, Turk DC, Adherne WA, Bird T, Holdaway MD, Court SDM. Deaths associated with respiratory tract infection in childhood. Br Med J 1967;4:316-20.

  7. MacDonald NE, Hall CB, Suffin SC, Alexson C, Harris PJ, Manning JA. Respiratory syncytial viral infection in infants with congenital heart disease. N Engl J Med 1982;307:397-400.

  8. Hall CB, Douglas RG Jr, Geiman JM, Messner MK. Nosocomial respiratory syncytial virus infections. N Engl J Med 1975;293:1343-6.

  9. Garner JS, Simmons BP. Guideline for isolation precautions in hospitals. Infect Control 1983;4(4 suppl):245-325.

  10. Williams WW. Guideline for infection control in hospital personnel. Infect Control 1983;4(4 suppl):326-49.



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