Japan’s National International Health Regulations Focal Point (NFP) notified WHO of an ongoing outbreak of measles in Japan.
From 1 January through 20 May 2018, 161 cases of measles were diagnosed, including 145 (90%) laboratory-confirmed cases.
Cases were reported from the following prefectures: Okinawa (88 cases); Aichi (25 cases); Fukuoka (17 cases); Tokyo (11 cases); Saitama (six cases); Ibaraki and Kanagawa (three cases from each prefecture); Yamanashi and Osaka (two cases from each prefecture); and Chiba, Shizuoka, Hyogo, and Yamaguchi (one case from each prefecture).
Among the total cases, to date, information for 30 cases regarding their isolated measles virus genotype have been received through the national surveillance system; excluding one case with vaccine strain, 25 were genotype D8 and four were genotype B3.
Cases of imported measles continue to occur in Japan. Japan has successfully eliminated endemic measles transmission and sustained this status since March 2015 through both high vaccination coverage and rapid detection of and response to every case of measles. In 2016, routine vaccination coverage was 97% for the first dose (one year of age) and 93% for the second dose (year before entrance to primary school, usually five years of age); serological surveys have confirmed that the proportion of antibody-positive (particle agglutination titer ≥16) individuals aged two years or more has remained at 95% or above nationally.
Measles is a highly contagious viral disease that remains one of the leading causes of mortality among young children globally, despite the availability of a safe and effective vaccine. Transmission from person-to-person is airborne, as well as by direct or indirect contact of secretions (nasal, throat) of an infected person. Initial symptoms, which usually appear 10–12 days after infection, include high fever, runny nose, bloodshot eyes, cough, and tiny white spots on the inside of the mouth. Several days later, a rash develops, starting on the face and upper neck and gradually spreads downwards. A patient is infectious four days before the start of the rash for up to four days after the appearance of the rash.