Health officials in Japan are combating the country’s worst measles outbreak in years, with many infections clustered among attendees of a Valentine’s Day gift fair and a religious group that avoids vaccinations.

A total of 167 cases were reported in 20 of Japan’s 47 prefectures as of Feb. 10, the National Institute of Infectious Diseases said, with the largest outbreaks in the prefectures of Mie and Osaka.

It is the fastest Japan has reached that many cases at the beginning of the year since 2008.

The flare-up of the highly contagious disease comes as the United States is grappling with measles outbreaks in Texas, New York and Washington, with more than 120 cases reported so far this year. Those outbreaks have prompted a rush to vaccinate children in some places where parents have broader choice over such decisions.

In Japan, almost all of the 49 reported cases in Mie Prefecture were people connected to Miroku Community Kyusei Shinkyo, a religious group that promotes alternative healing.