Reye Syndrome Surveillance -- United States, 1986

For the 1986 surveillance year (December 1, 1985-November 30, 1986), 101 cases of Reye syndrome (RS) were reported to the CDC National Reye Syndrome Surveil lance System (NRSS). All met CDC's case definition.* In the past, influenza B has been associated with an increased incidence of RS. However, from December 1985 through November 1986, a period that encompassed widespread influenza B activity, the number of RS cases reported was less than half the lowest number previously reported during a year with extensive influenza B activity. In addition, the reported number of varicella-associated RS cases (5) was the lowest since continuous national Reye syndrome surveillance began in 1977 (Table 1).

Thirty states and the Pacific Island Territories reported cases. Distributions by sex and race were similar to those of previous years: 52% of patients for whom this information was reported were female; 88% were white; 8%, black; and 4%, Asian or Pacific Islanders. Thirty-eight percent of patients with RS were 0-4 years of age; 12%, 5-9 years; 34%, 10-14 years; 15%, 15-19 years; and 2%, greater than or equal to20 years. Despite heavy influenza B activity in early 1986, the reported incidence of RS among childrenless than 10 years of age was lower that year than in 1985. However, the incidence of RS among children greater than or equal to10 years of age was higher in 1986.

Consistent with previous temporal associations between incidences of RS and influenza, 74% of patients reported in 1986 were hospitalized during January, February, and March, the peak months of influenza B activity. Early 1986 had, by several measures, the most widespread influenza B activity in the past 10 years (1). Compared with the other recent influenza B seasons--1979/80, a season of relatively heavy influenza virus activity; 1981/82, a season of minimal influenza virus activity; and 1983/84, a season of combined A(H1N1) and B activity--the 1985/86 season showed a decline in incidence of RS for all age groups, with the smallest decline being in the 15- to 19-year age group.

Ninety-two patients (91%) had an antecedent illness within 3 weeks before the onset of vomiting or neurologic symptoms compatible with RS. For 74% of these patients, the antecedent illness was primarily respiratory. Five percent had had varicella; another 5%, diarrhea without respiratory symptoms; 10%, fever or nonvaricella rash without respiratory symptoms; and 5%, other or unknown signs and symptoms.

Most patients were admitted to hospitals in the three precomatose stages of RS: 3% in stage 0, 36% in stage 1, and 40% in stage 2. Twenty-two percent of the 93 patients whose most severe stage of RS was reported reached only stage 1; 25% reached stage 2; 8%, stage 3; 6%, stage 4; 27%, stage 5. Thirteen percent receivedtreatment that precluded classification. Twenty-five of the 92 patients with reported outcome died, for a fatality rate of 27%. Reported by: Div of Viral Diseases, Center for Infectious Diseases, CDC. Editorial Note: Although the number of cases reported to the NRSS is presumably less than the true number of cases occurring in the United States each year, the NRSS provides crude annual comparisons of RS activity. Since a major multicenter study on RS (Public Health Service (PHS) Main Study on Reye Syndrome and Medications) was carried out during 1985 and 1986, it is unlikely that the decline in number of cases reported is an artifact of decreased reporting over these years.

The total number of reported cases of RS for 1986 is lower than would be expected based on influenza B activity during previous years. Although the number of cases reported in 1986 is slightly higher than that reported in 1985, the 1986 total is less than 30% that reported for any previous year with extensive influenza B activity and less than half the total for 1982, when there was a very low level of influenza B activity (Table 1). By available surveillance parameters, influenza B activity was heavier during the 1985/86 season than during any previous season for which simultaneous RS surveillance was conducted (1). Also, the number of reported varicella-associated RS cases was unusually low despite evidence of relatively stable national varicella activity (2).

Both the pilot phase of the PHS study on RS and medications, published in 1985, and the main study, published in 1987, have confirmed prior reports of an association between ingestion of aspirin during an antecedent viral illness and subsequent development of RS (3,4). Since the increasing publicity about the association between RS and aspirin began in late 1980, much of the decline in the reported incidence of RS in the United States may be attributable to possible decreases in the frequency and/or dose of this medication used in treating children with influenza-like illness or varicella (4-6).

Preliminary results from 1987 surveillance indicate further decreases in the reported number of RS cases in the United States. As RS becomes increasingly rare in this country, interest in reporting may also start to wane. Health-care personnel and agencies are urged to continue reporting to the NRSS to assure the best possible epidemiologic monitoring of this illness. In addition, physicians, parents, and older children who self-medicate should be aware of the increased risk of RS associated with using aspirin (and possibly all salicylates) to treat children, including teenagers, with influenza-like illness or chickenpox (varicella). RS cases should be reported through local and state health departments to the Reye Syndrome Surveillance System, Division of Viral Diseases, Bldg. 6, Rm. 115, Centers for Disease Control, Atlanta, Georgia 30333.

References:

1. CDC. Influenza--United States, 1985-1986 season. MMWR 1986;35:470,475-9.

2. CDC. Summary of notifiable diseases, United States, 1986. MMWR 1987 (in press).

3. Hurwitz ES, Barrett MJ, Bregman D, et al. Public Health Service study on Reye's syndrome and medications: report of the pilot phase. N Engl J Med 1985;313:849-57.

4. Hurwitz ES, Barrett MJ, Bregman D, et al. Public Health Service study of Reye's syndrome and medications: report of the main study. JAMA 1987;257:1905-11.

5. Remington PL, Rowley D, McGee H, Hall WN, Monto AS. Decreasing trends in Reye syndrome and aspirin use in Michigan, 1979 to 1984. Pediatrics 1986;77:93-8.

6. Barrett MJ, Hurwitz ES, Schonberger LB, Rogers MF. Changing epidemiology of Reye syndrome in the United States. Pediatrics 1986;77:598-602. *The CDC case definition is (1) acute noninflammatory encephalopathy documented by alteration in the level of consciousness and, if available, a record of cerebrospinal fluid containing eight leukocytes or less per mm3, or histologic sections of the brain demonstrating cerebral edema without perivascular or meningeal inflammation; (2) hepatopathy documented by either biopsy or autopsy considered to be diagnostic of RS or by a threefold or greater rise in the levels of either serum glutamic-oxaloacetic transaminase (SGOT), serum glutamic-pyruvic transaminase (SGPT), or serum ammonia; and (3) no more reasonable explanation for the cerebral or hepatic abnormalities.

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