Measles -- United States, 1985

Through December 28, 2,704 cases of measles in the United States were reported to MMWR for 1985. Detailed information reported to CDC's Division of Immunization is available for a provisional total of 2,813 cases for 1985, which includes some late reported cases. The 2,813 cases represent an 8.7% increase over the 2,587 cases reported in 1984. The overall incidence rate increased from 1.1 cases per 100,000 population in 1984 to 1.2/100,000 in 1985. Ten states accounted for 2,106 (74.9%) cases: Texas (443 cases), Illinois (360), California (270), Arizona (240), Washington (174), Montana (139), Idaho (132), Massachusetts (118), Maryland (115), and Florida (115). Ten reporting areas had incidence rates greater than 2/100,000 population: Arizona, District of Columbia, Hawaii, Idaho, Illinois, Maryland, Massachusetts, Montana, Texas, and Washington. During 1984 and 1985, 14 and 12 states, respectively, reported no measles cases (indigenous or imported). Of the nation's 3,139 counties, 220 (7.0%) reported measles cases in 1985, compared with 210 (6.7%) in 1984.

Of the 2,813 cases, 2,718 (96.6%) met the standard case definition for measles,* and 1,071 (38.1%) were serologically confirmed. Most of the patients (68%) had rash onset between weeks 8 and 25 (weeks ending February 23 and June 22) (Figure 4).

In 1984, the highest incidence rate was reported among children 10-14 years of age (Table 3). By comparison, in 1985, the highest incidence rate occurred among preschool-aged children (4.7/100,000), followed by persons 15-19 years of age (4.5/100,000). Of the 826 preschool-aged children with measles, 211 (25.5%) were infants under 1 year of age; 143 (17.3%) were 12-14 months of age; 41 (5.0%) were 15 months of age; and 431 (52.2%) were 16 months-4 years of age.

The setting of transmission was reported for 1,864 (66.3%) measles patients: 1,129 (60.6%)--school**; 278 (14.9%)--home; 87 (4.7%)--medical settings; 94 (5.0%)--day care; 94 (5.0%)--church; and 182 (9.8%)--other (including sporting events and summer camp). Of the 2,813 total cases, 354 (12.6%) were reported on 26 college campuses (Table 4).

One hundred twenty-one cases (4.3%) were international importations. An additional 166 (5.9%) cases were epidemiologically linked to an international importation within two generations of infection. Therefore, 287 (10.2% of all cases) were classified as international importations during this period (1).

Vaccination status of patients in 1984 and 1985 was similar. Of the 2,813 measles patients in 1985, 1,239 (44.0%) had been appropriately vaccinated (on or after the first birthday); 381 had been vaccinated at 12-14 months of age (Table 5). A total of 1,442 measles patients were unvaccinated, and 132 had histories of inadequate vaccination (vaccinated before the first birthday).

Of the 2,804 cases with known preventability status, 820 (29.2%) were classified as preventable (1). The highest proportion of preventable cases occurred among persons who were not of school age: 73.8% of cases among children 16 months-4 years of age were preventable (Table 6). Only 21.7% of cases among school-aged persons (5-19 years of age) were preventable. However, 347 (42.3%) of all 820 preventable cases occurred in this age group.

Of the 1,984 nonpreventable cases, 395 (19.9%) were among children too young for routine vaccination (under 16 months of age), and 71 (3.6%) persons were too old (born before 1957). Of the 1,518 between 16 months and 28 years of age, 1,207 (79.5%) had been vaccinated on or after the first birthday; 14 (0.9%) had a prior physician diagnosis of measles; 48 (3.2%) were non-U.S. citizens; and 248 (16.3%) had medical contraindications or other exemptions under state law (Table 7). Reported by Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: In the prevaccine era, an average of 500,000 cases were reported each year (2). Since measles vaccine was licensed in 1963, the incidence of measles has declined markedly. While the number of cases increased 8.7% from 1984 to 1985, the provisional total of 2,813 cases still represents only 0.6% of the average number of reported cases in the prevaccine era. Since 1981, the reported occurrence of measles has stabilized between approximately 1,500 and 3,200 cases. However, slight increases have been noted annually since the record low 1,497 cases reported in 1983.

The highest incidence rate in 1985 occurred in the preschool-aged population, which accounted for approximately 30% of all reported cases. Recent outbreaks involving a substantial proportion of preschool-aged children have also occurred (3,4). The increased incidence of measles among preschoolers is a source of concern, since the risk of serious complications of measles illness is highest in the youngest age groups (2). Seventy-four percent of cases among children 16 months to 4 years of age were preventable, emphasizing the need to vaccinate children promptly at the recommended age for routine vaccination (15 months).

The next highest incidence rate in 1985 occurred among persons 15-19 years of age, who accounted for another 30% of total cases. The increased rate in this age group over 1984 was due in part to the large number of outbreaks on college campuses. The proportion of total cases occurring on college campuses in 1985 was higher than that of any of the previous 6 years, except 1983 (Table 4). An increased number of colleges and universities are now requiring evidence of immunity to measles for matriculation, which should decrease measles in this population (5).

Persons of school age accounted for the largest percentage of all preventable cases, and schools were the setting of transmission for the majority of cases. Therefore, continued enforcement of current school immunization laws is important for further reduction of measles in the United States.

References

1. CDC. Classification of measles cases and categorization of measles elimination programs. MMWR 1982:31:707-11.

2. CDC. Measles surveillance report no. 11, 1977-1981. Atlanta, Georgia: Centers for Disease Control, 1982.

3. CDC. Measles--Arizona. MMWR 1986;35:99-100, 105-7.

4. CDC. Measles--New Jersey. MMWR 1986;35:213-5.

5. CDC. Measles on college campuses--United States, 1985. MMWR 1985;34:445-9. *Fever (38.3 C (101 F) or higher, if measured); generalized rash lasting 3 or more days; and at least one of the following: cough, coryza, conjunctivitis. Includes kindergarten through college.

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