An epidemic of measles, September 1998-October 1999 - Okinawa
(IASR 1999; 20: 275-275)

Measles epidemic was observed in Okinawa Prefecture during September 1998 to August 1999. The epidemics have also recorded in 1990 and 1993. This time the epidemic started in Chubu in the central region in September 1998, and incidence also made a small peak in December. After that, the incidence once dropped, but the disease spread the whole prefecture. Large incidence peaks were observed in Chubu region during March and April, 1999, followed by Nambu in the southern region in June. The epidemic has continued for a year, and it ceased in August.

Pediatricians working 3 general hospitals in Okinawa Prefecture counted hospitalized measles patients during this epidemic. In total 675 children were hospitalized including 227 (34%) less than 12 months old, 244 (36%) in one year old. The incidence decreased gradually as age becomes elder to 15 years old. Of 227 infant cases, 30 cases (4.4%) were under 6 months old and 6 cases were under 1 month old. Vertical transmission from mother was observed in some cases. The incidence among 4-5 months old might have related with early depression of maternal antibody, however, it was not confirmed.

Pneumonia (65%), gastroenteritis (18%), and croup (11%) were major complications. Of 8 fatal cases (1.2%), 6 cases complicated severe pneumonia, one complicated encephalitis, and the other one case developed both. Virus-associated hemophagocytic syndrome (VAHS) was observed in 0.4% of the cases. Age distribution of these fatal cases included 3 under 1 year old, 3 one year old, one 2 years old, and one 3 years old with cerebral palsy. Adeno virus 7 was isolated in Okinawa during March to July 1999, possibility of concurrent infections were pointed out.

Ninety-eight percent of the hospitalized patient was not immunized with measles, included those who received vaccine during incubation period. Vaccine failure was estimated 2.5%. Vaccination was thus supposed to control the epidemic. Vaccination might as well be given twice considering vaccine failure. In Chubu region unscheduled measles vaccination was conducted to those who wished the shot over 9 to 12 months old. Under the current immunization law, measles immunization is given to infant after one year birthday.

Nosocomial infection, especially at the out-patient department or the ward was suspected as main mode of infection. Hospital A estimates 44%, and hospital B does 29% of the measles cases attributed to nosocomial infection. It is difficult to prevent measles infection from a patient in catarrhal phase, unless giving vaccine previously. In order to prevent nosocomial infection, measles patients were isolated, and gamma globulin was administered to hospitalized patients, when exposure to the measles patients was suspected.

Low measles vaccination rate is pointed out as the primary cause of this epidemics., Reported vaccination rate in Okinawa Prefecture is 61% in 1997. The rate varied in the region, and the rate is under 50% in some regions. According to investigation by the Pediatric Hygiene Association of Okinawa Prefecture, the vaccination rate at health check at 18-month old was 63% and 84% at 3-year old, respectively. The vaccination rate is not high enough to suppress the measles epidemics.

The Prefecture's Advisory Committee for Immunization imperatively investigated magnitude of the epidemic, as well as appealed measles vaccination using mass media. In addition, the Committee decided to strengthen 1) communicable disease surveillance, 2) health education and vaccination at health check to infants and children entering kindergarten, 3) catch-up vaccination, 4) designation of immunization center for the high risk vaccinees. Such efforts should reduce the incidence of measles and eradicate the disease.

Reported by Hideki Akeda, Dept. Pediatrics, Okinawa Prefectural Naha Hosp; Moriyasu Kohama and Kaoru Ashimine, Dept. Pediatrics, Okinawa Prefectural Chubu Hosp; Ryuji Ishihara and Ei-ichi Tamanaha, Dept. Pediatrics, Nakagami Hosp; Suzuka Toguchi and Masao Chinen, Dept. Pediatrics, Naha Municipal Hosp.

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