Tokyo: Japan has entered the influenza season nationwide, the health ministry said Wednesday.

The nationwide flu spread came for the first time in three years. As COVID-19 is also continuing to spread, the ministry is increasingly concerned about a “twindemic.”

The ministry made the announcement based on reports from 5,000 regularly monitored medical institutions across the country.

In the week through Sunday, the number of flu patients surged more than twofold from the previous week to 6,103, or 1.24 per reporting institution.

The ministry declares a flu epidemic if the per-institution figure exceeds one.

According to the ministry and other sources, the number of flu patients was estimated at 7.29 million in the 2019-2020 season. Amid the COVID-19 pandemic, the estimated number plunged to 14,000 in the 2020-2021 season and 3,000 in the 2021-2022 season.

As a result, the number of people with immunity against seasonal influenza is believed to have significantly decreased.

JIJI Press