Measles -- Hawaii

Between May 5, and June 29, 1984, 106 cases of measles were reported on the island of Kauai, Hawaii (Figure 3). All met the clinical case definition* for measles; 25 cases were serologically confirmed.** Four distinct generations of illness were identified 10-12 days apart. The second generation (May 17-28) was the largest, with 35 (33%) cases. No source was identified. Seven children (7%) of the 106 patients were hospitalized secondary to measles. Three were hospitalized for diarrhea and dehydration, and four, for evaluation.

The single largest group of cases, 52 (49%), occurred among children under 5 years of age, including 36 (34%) under 16 months of age (Table 4). Persons 15-19 years of age were the next largest group, accounting for 27 (25%) cases. Forty-five (42%) of the cases occurred among school-aged children (5-19 years). Although more than two-thirds of the first generation occurred among school-aged children (15/22), the second generation occurred mainly in preschool-aged children 0-4 years of age (25/35). Further investigation revealed that 16 (46%) of the 35 second-generation cases were among infants 15 months of age or younger,*** compared to two (9%) of 22 cases in the first generation. High school students accounted for 34 (75%) of the school-aged patients. Seven additional cases occurred at four elementary schools.

Of the 106 cases, 48 (45%) were considered preventable**** (Table 5). Thirty-two of these patients had no record of measles vaccination or prior physician-diagnosed natural disease, and 16 had been vaccinated at under 12 months of age. Thirty-six of the 58 nonpreventable cases***** (62%) occurred among children 15 months of age or younger, most of whom were too young for routine vaccination. Eighteen (31%) of the nonpreventable cases had been immunized appropriately.****** The remaining four measles patients were 28 years of age or older--too old for routine vaccination. Of the 45 school-aged patients, 16 (35%) were vaccinated at 12 months of age or under; 12 (27%) were unvaccinated. Thus, non-immune schoolchildren accounted for 58% (28/48) of all preventable measles cases.

Sixteen persons who subsequently developed measles had visited a doctor's office in May and June at the same time a patient with known or suspected measles was being seen in the office; one additional person was seen within 45 minutes after a patient with known measles left the office. All such visits occurred 8-14 days before onset of rash. Sixteen of the cases were in children; one was in a parent of one of these children. Mothers of four recalled face-to-face contact in the waiting room between their children and another child with rash. In 12 cases, for which exact times were available, the exposed person had been in the office with the measles patient for 20-90 minutes. No other possible sources of measles exposure were identified for these 17 cases. Interviews with parents revealed that, of the 16 children involved in office transmission, two were in the office primarily for measles-mumps-rubella vaccine, and four, for routine examination; four accompanied an ill relative; and seven were ill themselves. Transmission in physicians' offices was most important in infecting young preschool-aged children. Such transmission accounted for 36% of cases among children 15 months of age and under and 31% of cases among children under 5 years of age.

Interviews with office staff revealed that procedures for isolating sick children from well children in the office were not well implemented. In many cases, parents brought in their children complaining of high fever and rash without appointments and either had to wait in or pass through a common waiting room.

On June 6, because of increasing evidence that up to one-third of all measles cases were occurring among children under 15 months of age, measles vaccination recommendations were extended to children as young as 6 months of age for the duration of the outbreak. On June 7, to limit measles transmission in private offices, the Hawaii Department of Health recommended that health professionals: (1) screen patients requesting appointments by asking if symptoms of rash and fever were present. If possible, such patients should then be seen in separate facilities or at the end of the day after all other patients had left; (2) keep suspected measles patients in respiratory isolation in separate rooms with face masks to limit spread of the virus; they should be given priority and seen as soon as possible.

Although measles cases continued to be reported in June and July, the last case of suspected intraoffice transmission occurred on June 7. With the implementation of isolation precautions and continued vaccination of susceptible children and adults, reports of measles cases began to decline after the third generation (Figure 3).

To define other populations at risk for disease, an island-wide school and day-care center health record review was done. A student was considered susceptible to or at high risk for measles if there was no record of receipt of live measles vaccine on or after the first birthday and no record of physician-diagnosed measles. Using this definition, 47% (1,864/3,986) of high school students and 22% (1,109/5,100) of elementary, private, and parochial school students were considered susceptible. Those students were asked to provide proof of previous adequate vaccination or be vaccinated in school-based clinics, held in all three high schools before graduation and end of school or in public clinics. Over 1,000 students were vaccinated at the high school clinics. Approximately 400 persons were vaccinated in 13 public clinics held between June 7 and June 15 for the general public and elementary and private schools. Reported by H Michioka, SMD Terrell-Perica, P Tokita, M Tsuchiya, T Inouye, Kauai District Health Office, K Corrigan, A Hendersen, CM Ibara, G Kobayashi, R Salcido, C Wakida, A Liang, MD, State Epidemiologist, Hawaii State Dept of Health; Div of Field Svcs, Epidemiology Program Office, Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: Over the last 5 years, Hawaii has made significant progress towards measles elimination. The last major cluster of measles cases occurred in 1979, when 68 cases were reported. Fewer than seven cases had been reported annually in Hawaii since 1980. The present outbreak confirms that measles can occur in populations essentially free of disease for long periods. The source of this outbreak was not determined.

Hawaii's immunization law, enacted in 1974, covers only new school enterers and has been vigorously enforced only since about 1976. In this outbreak, susceptible schoolchildren made up 62% (28/45) of all school-aged measles patients. The predominance of high school students among the school-aged patients may, in part, reflect a higher susceptibility rate among the age group that was too old to be affected by the law. Only the year of vaccination was required for the school record. Considerable numbers of susceptibles were identified, because many students had records of vaccination in the year of, or the year following, birth, making determination of who was vaccinated on or after the first birthday impossible. Vigorous enforcement of comprehensive school laws covering all students from kindergarten through grade 12 has been demonstrated to be the most effective means of reducing measles incidence rates (1).

This outbreak is also important because of the large number of preschool-aged children who acquired measles. Of the 52 preschool-aged children with measles, 69% were under 16 months of age and their cases, therefore, were nonpreventable. However, 15 children in the preschool-aged group simply had not been vaccinated, and their measles could have been prevented (Table 5).

This investigation suggests that transmission in physicians' offices played a major role in perpetuating the outbreak, particularly among children too young for routine vaccination. Intraoffice transmission can occur both when droplet nuclei are aerosolized by coughing children and by direct physical contact between children. Measles outbreaks in medical offices, airports, and other settings have been propagated by susceptible persons inhaling measles-containing droplet nuclei left by infected persons (2-4). Transmission in medical offices has been documented to have occurred up to 75 minutes after an infectious person has left the office (5). The opportunity for intraoffice transmission by both direct contact and airborne routes was present on Kauai.

In situations where exposure has already occurred, susceptible persons who had face-to-face contact with a measles patient may benefit from immune globulin prophylaxis, if it is given within 6 days of exposure. Measles vaccination may provide protection if it is given within 72 hours of exposure. Prophylaxis is not generally offered to persons who have not had face-to-face contact but were in the office with the patient or arrived after the patient departed. The rarity of reports of transmission in doctors' offices suggests that airborne transmission is uncommon. Denominator data that would have defined the actual risk of measles for patients in a physician's office in this outbreak are lacking. However, should future outbreaks

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