National Reye Syndrome Surveillance -- United States, 1982 and 1983

For the 1982 and 1983 surveillance years,* CDC received written reports of 222 and 191 cases of Reye syndrome, respectively, that met CDC's case definition.** Cases were reported from 45 states in 1982 and 38 states in 1983. Although delayed reports will increase the number of cases for 1983, these two annual totals are presently the lowest reported since continuous national surveillance was established in December 1976 (Table 1).

The sexes, ages, and racial distribution of patients were very similar in 1982 and 1983. Of patients for whom this information was reported, approximately 50% were female; approximately 93%, white; 5%, black; and 1%-2%, of Asian extraction. Over half (56% in 1982 and 51% in 1983) were 5-14 years of age; 37% and 40%, respectively, in each of the 2 years were 4 years of age or under; 6% and 7%, respectively, 15-17 years of age; and 1% and 3%, respectively, 18 years of age or older.

As in previous years, most patients (at least 67% in 1982 and 74% in 1983) were hospitalized in the first 6 months of the surveillance year. This primarily winter and spring seasonal distribution of cases reflected the seasonality of respiratory viral infections among children, particularly influenza (predominantly influenza type B in 1982 and type A(H3N2) in 1983) and varicella (Figure 1). For 196 (88%) of the patients in 1982 and 175 (92%) in 1983, a type of prodromal illness experienced within 2 weeks before onset of vomiting or neurologic symptoms of Reye syndrome was reported. For each of these 2 years, the prodromal illness was characterized by respiratory symptoms (57% and 73%, respectively), varicella exantham (24% and 14%, respectively), diarrhea without respiratory symptoms (4% in both years), or other signs or symptoms, including fever alone (15% and 9%, respectively).

As reported in earlier years, the majority of patients (80% in 1982 and 79% in 1983) were admitted to hospitals in precomatose stages of Reye syndrome, stages 0, 1, or 2. Although these proportions are slightly higher than those reported before 1980, they represent a decline from the peak (86%) reached in 1981. In 1982 and 1983, the plurality of patients by stage of admission was stage 2 (34% and 40%, respectively, of the approximately 95% of patients each year for whom this information was reported). The second most frequently reported stage of admission was stage 1 (32% in 1982 and 30% in 1983).

The short-term outcome was reported for 208 (94%) of the 222 Reye syndrome patients in 1982 and 173 (91%) of the 191 patients in 1983. The case-fatality ratios for these 2 years were 35% and 32%, respectively (Table 1). Reported by Div of Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: The numbers of both nonfatal and fatal cases of Reye syndrome reported through the national surveillance system are useful in providing crude annual comparisons but probably underestimate the true incidence and mortality of this illness. Because state health departments and CDC are more likely to become aware of fatal cases, the reported case-fatality ratios are probably overestimates.

The relatively low reported incidence of Reye syndrome in 1982 and 1983 probably reflects, at least in part, the intensity and/or type of influenza activity. In terms of all available criteria, the intensity of influenza B activity in early 1982 was low (1). The intensity of influenza activity in 1983 was greater, although not as great as in 1980-1981, and the predominant isolate was influenza A(H3N2), which has been previously associated with fewer large clusters of Reye syndrome than influenza B.

The apparent drop in varicella-associated cases in 1982 (47 cases) and 1983 (25 cases) is currently less well explained by changes in virus activity; 83 such cases were reported in 1981. From 1977 through 1982 (the years for which data are most recently available), the reported incidence of varicella itself has remained relatively stable.

The intensity of Reye syndrome surveillance varies by both geographic area and year, and hence, changes in reported incidence must be cautiously interpreted. The intensity of surveillance usually depends, in part, on the awareness of the illness among the public and medical personnel and the ease and perceived importance of reporting cases. The relatively low reported incidence of Reye syndrome in 1982 and 1983 occurred during a period of increased publicity about the reported association between Reye syndrome and the use of salicylates for children with chickenpox or influenza-like illness (2).

As of January 27, 1984, increasing numbers of states have reported influenza virus isolates, type A(H1N1) predominantly, as well as types A(H3N2) and B. Physicians and other appropriate personnel in the medical community are encouraged to continue reporting Reye syndrome cases to CDC through their local and state health departments. Reye syndrome case-report forms can be obtained from state health departments or CDC, c/o Epidemiology Office, Division of Viral Diseases, Atlanta, Georgia 30333.

References

1. CDC. Influenza surveillance summary, 1981-1982 season. MMWR 1982;31:375-8.

2. CDC. National surveillance of Reye syndrome 1981: update, Reye syndrome and salicylate usage. MMWR 1982;31:53-6. *For the purposes of surveillance, Reye syndrome years extend from December 1 to November 30 (i.e., the 1982 year runs from December 1, 1981, to November 30, 1982). The data for 1983 are preliminary. **The CDC case definition is (1) acute noninflammatory encephalopathy documented by the clinical picture of alteration in the level of consciousness and, if available, a record of cerebrospinal fluid containing 8 leukocytes or less per mm((3)), or histologic sections of the brain demonstrating cerebral edema without perivascular or meningeal inflammation, (2) fatty metamorphosis of the liver diagnosed by either biopsy or autopsy or a threefold or greater rise in the levels of either the SGOT, SGPT, or serum ammonia, and (3) no known more reasonable explanation for the cerebral or hepatic abnormalities.

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