Japan is on pace this year to log its highest number of annual measles cases since the end of the COVID-19 pandemic, with 236 patients confirmed by early April compared with the post-pandemic full-year high of 265 marked last year.

About half of patients are age 10 to 29, and the Japan Pediatric Society is calling on people to get vaccinated.

People with measles experience symptoms similar to those of a cold about 10 days after infection, followed by a high fever and a rash. Almost all infected people without immunity develop symptoms, and the illness can lead to severe complications such as encephalitis and pneumonia.

Japan was certified by the World Health Organization in 2015 as being free of indigenous measles viruses, but infections continue due to viruses that arrive from abroad.

According to the WHO, the number of reported measles cases across the globe increased from around 60,000 in 2021 to approximately 360,000 in 2024, with outbreaks occurring in the United States, Africa and Southeast Asia in recent years.

The Japan Institute for Health Security said that the largest number of annual patients in Japan in the past decade is 744 in 2019. The number fell sharply between 2020 and 2022, when border control measures were strengthened due to the COVID-19 pandemic, but started to increase after borders were reopened in full.

Between January and early April this year, Tokyo had the highest number of patients among the country¡¯s 47 prefectures, at 72, followed by Kagoshima at 27 and Aichi at 23.

People in the 10-19 age group accounted for 24% of the patients, and those in their 20s made up 28%. Half of all patients were not fully vaccinated or had no known history of vaccination.

The risk of developing symptoms and becoming seriously ill can be greatly reduced by two routine measles vaccinations. The first shot is given at the age of 1 and the second shot is administered before children enter elementary school. Some people in their late 30s to 40s received only one regular vaccination and therefore do not have sufficient immunity.

The JPS is urging people to check their vaccination records and to consider receiving shots if they are found to have been unvaccinated or have no known records, noting that some people from age 10 to 29 may have not completed their routine vaccinations.