During the first 26 weeks of 1990, a total of 266 measles cases* (incidence: 5.8 cases per 100,000 population) was reported to the Washington State Department of Health from 15 (38%) of the state's 39 counties. This number is nearly five times the total reported statewide during all of 1989 (55 cases) and is the largest number of cases reported by the state during any year since 1979. Seventy-five (28%) of the reported cases were serologically confirmed. Detailed data were available for 218 cases reported during the first 22 weeks of 1990.

Of the 218 cases, 97 (45%) were in Hispanics (58 cases per 100,000); 14 (6%), American Indians (20 cases per 100,000); 100 (46%), non-Hispanic whites (3 cases per 100,000); five (2%), blacks (3 cases per 100,000); and two (1%), Asians (1 case per 100,000). Of the 97 Hispanic patients, 70 (72%) were Mexican citizens and 27 (28%) were U.S. citizens (Table 1).

One hundred one (46%) patients were less than 5 years of age, including 51 aged less than 16 months; 50 (23%) were aged 5-19 years; 67 (31%) were aged greater than or equal to 20 years, including 16 who were born before 1957 (Table 2). Children less than 5 years of age had the highest age-specific incidence rate (29.2 per 100,000) (Table 2). Of the 97 Hispanic patients, 59 (61%) were less than 5 years of age, including 32 who were less than 16 months of age.

Forty-nine (23%) patients had been vaccinated, including three who were vaccinated 2, 3, and 10 days, respectively, after exposure (Table 1). Of the 169 unvaccinated patients, 98 (58%) should have received vaccine according to routine indications**, 54 (32%) were less than 16 months of age, 11 (7%) were born before 1957, and six (4%) had religious or philosophic exemptions. Of the 98 unvaccinated patients for whom vaccine was indicated, 45 (46%) were Hispanic Mexican citizens, five (5%) were Hispanic U.S. citizens, 46 (47%) were non-Hispanic U.S. citizens, and two (2%) were non-Hispanic visitors from other countries.

Fifteen (7%) cases were in persons infected in Mexico and were linked to 41 (19%) additional cases. Sixteen cases were in persons from other states and were linked to two additional cases.

At least 37 (17%) persons acquired measles through exposure in medical settings (three in physicians' offices, four on hospital wards, and 30 in emergency rooms). These persons included 16 medical workers, who infected at least six other persons (including three hospital patients). Serosurveys conducted at two hospitals as part of vaccination programs indicated that 119 (7%) of 1698 employees lacked immunity as defined by enzyme-linked immunosorbent assay. None of the 19 hospitals where patients were treated had an employment policy requiring measles immunity.

Many patients with measles were not isolated promptly because of initial mis diagnosis. At least nine measles patients at three hospitals presented with fever, cough, conjunctivitis, and rash but were initially diagnosed as having hepatitis, viral syndrome, drug reaction, or Kawasaki disease. They remained in emergency rooms for up to 13 hours, were hospitalized without isolation, or were sent home where additional exposures occurred in family members. At least 31 cases in family members, other hospital patients, visitors, or staff were linked to these nine patients.

Two persons aged 30 and 36 years, respectively, died from measles-related pneumonia (case-fatality rate: 9.2 deaths per 1000 cases), representing the first measles-related deaths in Washington since 1978. Fifty-nine (27%) patients were hospitalized for a total of 236 days.

To control this epidemic, the Washington State Department of Health provided greater than 76,000 doses of measles vaccine, at a cost of $1.1 million, for use in vaccination clinics. These clinics were publicized in Spanish and English on radio and television, in newspapers, and by sound trucks driven through areas having a high proportion of Hispanic residents. In one severely affected county, the recommended age for measles vaccination was lowered to 12 months. In addition, susceptible students and staff were excluded from attendance at all 15 schools where at least one case occurred; at 13 of these schools, there was no evidence of secondary transmission. At one of the two schools where secondary transmission occurred, all students were vaccinated. Reported by: L Jecha, MD, Benton-Franklin Health District; R Alexander, MD, Seattle-King County Dept of Public Health; C Winegar, Tacoma-Pierce County Health Dept; M Patnode, R Atwood, MD, Yakima Health District; R Nelson, B Baker, Immunization Program Office, JM Kobayashi, MD, State Epidemiologist, Washington State Dept of Health. Div of Field Svcs, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: Two factors that contribute to the occurrence of measles outbreaks in the United States are the continuing importation of measles and the transmission of measles in medical settings (1-4). In the Washington epidemic, 26% of cases were acquired in Mexico or epidemiologically linked to these cases. In contrast, in the United States in 1989, 3% of cases were associated with importations (5). Seventeen percent of cases in the Washington epidemic were acquired in medical settings.

In Washington, Hispanics constitute 4% of the total population and are the largest ethnic minority group in the state. From 1980 through 1988, Washington's Hispanic population increased by an estimated 39% (6). Although measles vaccination coverage for the state's total Hispanic population is unknown, the high attack rate for Hispanics suggests that coverage is low.

Nearly half the cases in this epidemic occurred among unvaccinated persons for whom vaccine was indicated. Of these unvaccinated persons, more than half were Hispanic. Although vaccination programs should target all eligible persons, unique measles vaccination strategies are needed in those areas of the United States with large numbers of Hispanic persons who are recent immigrants, preschool-aged children, or undocumented residents. Vaccination clinics at churches and workplaces might reach undocumented residents who are reluctant to go to health departments or physicians' offices for vaccination. Any strategy should account for the potential reluctance of undocumented residents to have contact with government agencies.

Nosocomial transmission of measles continues to occur in the United States, in large part because measles cases are often not diagnosed and isolated promptly and because many medical workers are not immune (3,7). As in previous epidemics, a large proportion of the nosocomial transmission in Washington occurred in emergency rooms (3), possibly because emergency rooms are the primary source of medical care for many persons. Medical providers must be familiar with the clinical and epidemiologic features of measles, so that cases will be recognized promptly and patients isolated.

In Washington, the lack of hospital employment policies requiring immunity to measles accounted for disease in medical workers, major disruptions in staffing, substantial expenses for serologic testing and vaccination during the outbreak, and transmission from medical workers to others. In December 1989, Immunization Practices Advisory Committee (ACIP) recommendations were published that advised medical facilities to require all staff who will have direct patient contact to provide evidence of two live measles vaccinations, documentation of physician-diagnosed measles disease, or laboratory evidence of immunity (8).

References

1. Markowitz LE, Tomasi A, Hawkins CE, et al. International measles importations: United States, 1980-1985. Int J Epidemiol 1988;17:187-92.

2. Markowitz LE, Preblud SR, Orenstein WA, et al. Patterns of transmission in measles outbreaks in the United States, 1985-1986. N Engl J Med 1989;320:75-81.

3. Davis RM, Orenstein WA, Frank JA, et al. Transmission of measles in medical settings: 1980 through 1984. JAMA 1986;255:1295-8.

4. CDC. Measles--Los Angeles County, California, 1988. MMWR 1989;38:49-52,57.

5. CDC. Measles--United States, 1989 and first 20 weeks 1990. MMWR 1990;39:353-5,361-3.

6. Washington State Office of Financial Management. 1988 Population trends for Washington State. Olympia, Washington: Washington State Office of Financial Management, Forecasting Division, 1988.

7. Braunstein H, Thomas S, Ito R. Immunity to measles in a large population of varying age. Am J Dis Child 1990;144:296-8.

8. ACIP. Measles prevention: recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1989;38(no. S-9). *Illness with generalized rash lasting greater than or equal to 3 days, temperature greater than or equal to 38.3 C (greater than or equal to 101 F), and cough or coryza or conjunctivitis. **Vaccine is routinely indicated for persons born in or after 1957 who are greater than or equal to 16 months of age, lack evidence of immunity, have no medical contraindication to vaccination, and have no religious or philosophic exemption.

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