The largest measles outbreak including 38 modified measles and 22 typical measles cases Yamagata Japan 2017 in its elimination era.

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Jpn J Infect Dis. 2018 Jun 29. doi: 10.7883/yoken.JJID.2018.083. [Epub ahead of print]

The largest measles outbreak including 38 modified measles and 22 typical measles cases Yamagata Japan 2017 in its elimination era.

Komabayashi K¹ Seto J¹ Tanaka S¹ Suzuki Y¹ Ikeda T¹ Onuki N² Yamada K³ Ahiko T¹⁴ Ishikawa H⁵ Mizuta K¹.

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Abstract

Modified measles (M-Me) characterized by milder symptoms than typical measles (T-Me) has been increasing in Japan but M-Me dominated outbreak has not been investigated sufficiently worldwide. During March-April 2017 there was the largest importation-related outbreak of measles with genotype D8 in Yamagata Japan after Japan had achieved measles elimination in 2015. We confirmed 60 cases by detecting measles virus (MeV) genome among whom 38 M-Me and 22 T-Me cases were identified. Thirty-nine cases (65.0%) were between 20-39 years of age. Three out of seven primary cases produced 50 transmissions in which each patient caused 9-25 transmissions. They were aged 22-31 years with no vaccination developed T-Me and kept contact with the public during their symptomatic periods. Considering that M-Me is generally caused by vaccine failure some individuals with insufficient immunity for MeV might exist in Japan. Accordingly additional doses of measles vaccine may be needed especially for people aged 20-39 years to prevent measles importation and endemicity. Furthermore to correctly and rapidly diagnose measles especially to identify patients who could become primary cases efforts to detect all measles cases using epidemiological and genetic approaches should be made in countries where measles elimination had been achieved.

KEYWORDS:

Elimination era; Imported measles; Primary case; Vaccination

PMID: 29962488 DOI: 10.7883/yoken.JJID.2018.083