Measles is resurging in Japan at the largest scale since the COVID-19 pandemic, putting health authorities on high alert. With confirmed cases this year already exceeding four times the figure from the same period last year, concerns are growing that domestic transmission may be taking hold as infections without overseas travel history continue to emerge.
Japan's National Institute of Health Crisis Management reported 139 confirmed measles cases from the start of the year through June 15, according to Fuji News Network (FNN) and Kyodo News on Tuesday. The figure includes 32 new cases added in a single week, representing more than a fourfold surge compared with the same period last year, when 32 cases were recorded.
The tally marks the highest since the COVID-19 pandemic. Measles cases in Japan had peaked at more than 700 in 2019 before plunging to fewer than 10 during the pandemic years. Numbers have since climbed again, with 265 cases confirmed last year alone. The pace of increase is even steeper this year. Experts believe the virus was brought into the country by inbound travelers and returning residents before spreading domestically.
Measles is highly contagious, capable of airborne transmission. The infection rate exceeds 90% when an unvaccinated person comes into contact with a patient. Symptoms include fever, rash and cough, and severe cases can lead to encephalitis or death. Japan's Ministry of Health, Labour and Welfare has urged travelers to verify their vaccination records before departure and monitor their health for two weeks after returning.
South Korea is not immune to the threat either. According to the Korea Disease Control and Prevention Agency (KDCA), 39 measles cases were reported domestically as of April 12 this year, 2.1 times the 18 cases recorded during the same period a year earlier. Imported cases and secondary transmissions within households and medical facilities are being reported simultaneously. South Korea received WHO measles elimination certification in 2014, but sustained domestic transmission could jeopardize that status, as happened with Canada.
The measles resurgence is not limited to Japan. The United States recorded 2,274 confirmed cases last year, the highest in roughly 30 years, and hundreds of additional cases have been reported this year.
Canada saw its WHO measles elimination status revoked in November last year after continued domestic cases. The elimination designation requires at least 12 consecutive months without domestic transmission to be maintained.