About 300 people — 200 prisoners and 100 staff members — at Nagoya Prison in Aichi Prefecture have contracted the flu since late December, the prison said Thursday.

Even though none of the flu cases is severe at this point, the facility, which has a total of roughly 1,700 inmates, declared a state of emergency and temporarily suspended prisoner activities to allow inmates and staff to recover, and to stop the virus from spreading further.

Prisoners started showing symptoms of the flu around Dec. 20, and 205 inmates had contracted it by Wednesday, according to the prison, which is located in the city of Miyoshi.

The last time more than a hundred people at the prison caught the flu was in 2015 when 109 got sick.

Starting Jan. 26, the prison began taking the temperature of every inmate daily in an effort to alleviate the situation. Prisoner activities have been temporarily put on hold and inmates have been confined to their rooms since Monday. The prison began testing its entire staff for the flu the same day.

Every fall, the Justice Ministry cautions prisons to take precautions to stave off the onset of the flu. Since December, inmates and staff at Nagoya Prison have been advised to wear face masks and gargle, and 63 elderly individuals at higher risk have received vaccinations.