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Measles -- United States, First 39 Weeks, 1984

During the first 39 weeks of 1984, a provisional total of 2,322 measles cases was reported in the United States (incidence rate 1.0/100,000 population) (Figure 1). This is an 84.3% increase from the 1,260 cases reported during the same period in 1983 (0.5/100,000). Of the total, 1,620 cases (69.8%) were reported from five states--Texas (509), Michigan (462), California (308), Illinois (178), and Hawaii (163). Eleven states (California, Hawaii, Idaho, Illinois, Michigan, New Hampshire, New Mexico, Texas, Utah, Vermont, Washington) and New York City had incidence rates of 1.0/100,000 population or higher.

Although the overall incidence rate increased, the number of states reporting measles was similar to the number reporting during the same period of 1983. Seventeen states reported no measles cases (indigenous or imported), compared with 16 states and the District of Columbia during the same period in 1983. However, the increase in cases was associated with an increase in the number of counties affected. In 1984, 183 (5.8%) of the nation's 3,139 counties reported measles cases during the first 39 weeks, compared with 115 (3.7%) during the same period in 1983.

Two hundred sixty-two cases (11.3%) were associated with international or out-of-state importations--an average of 6.7 cases per week--compared with 220 (17.5) cases during the same period in 1983 (1).

During the first 39 weeks, detailed information was provided to CDC's Division of Immunization on 2,321 cases.* Of these, 2,277 (98.1%) met the standard clinical case definition for measles,** and 919 (39.6%) were serologically confirmed. In most cases, onset of rash occurred from weeks 9 through 21, peaking at week 14 (134 cases) (Figure 2).

The age characteristics of reported cases changed from 1983 to 1984 (Table 1). In 1983, the highest incidence rates were reported for preschoolers. In contrast, the rates for the first 39 weeks of 1984 were highest for children 10 years to 14 years of age, who had a more than threefold increase in incidence rates, compared with the total for 1983. Of the 569 preschoolers who had measles in 1984, 155 (27.2%) were under 12 months of age; 114 (20.0%) were 12-14 months of age; 38 (6.7%) were 15 months of age; and 262 (46.0%) were 16 months to 4 years of age. Persons 12-14 months of age accounted for 4.9% of the 2,321 cases.

Of the 2,321 cases, 819 (35.3%) were classified as preventableS (1) (Table 2). The highest proportion of preventable cases occurred among persons who were not of school age. Almost 75% of the cases among children 16 months to 4 years of age and adults 20-24 years of age were preventable. Although more than half the preventable cases occurred among persons 5-19 years of age, only 31.4% of cases occurring in that age group were considered preventable. The proportion of preventable cases in this group increased progressively with increasing age. Reported by Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: The increased number of cases from 1983 to 1984 and the increased geographic distribution indicate the need for careful and continued evaluation of the measles situation in the United States. Available information does not indicate the basic elimination strategy should be revised but does show a need for intensive application of the basic approach: achieving and maintaining high immunization levels, effective surveillance, and aggressive response to cases.

Of the 1984 measles patients, 38.1% had been adequately vaccinated. This is within expected limits, given the high vaccine coverage in the United States (2). The increased occurrence of measles in 1984 does not appear to be due to poor vaccine efficacy.

A substantial proportion of cases remains preventable. Greatest emphasis should be given to ensuring that school-aged individuals at all grade levels have evidence of measles immunity. In addition, assuring age-appropriate immunization of preschoolers remains important. Measles vaccine is indicated for all children 15 months of age or older unless there are contraindications. Measles immunity should also be a high priority in college-aged and other easily identifiable age groups.


  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. September 1982. *The difference between this number and the 2,322 cases reported to MMWR reflects delays in reporting. **Clinical case definition is fever (38.3 C (101 F) or higher, if measured), generalized rash of 3 days' duration or longer, and at least one of the following: cough, coryza, or conjunctivitis. ***A case is considered preventable if measles occurs in a U.S. citizen: (1) at least 16 months of age, (2) born after 1956, (3) lacking adequate evidence of immunity to measles (documented receipt of live measles vaccine on or after the first birthday and at least 2 weeks before onset of illness or physician-diagnosed measles or laboratory evidence of immunity), (4) without a medical contraindication to receiving vaccine, and (5) with no religious or philosophic exemption under state law.

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