Lowered Immunity After COVID Sees Unseasonal Flu Epidemic

The Yomiuri Shimbun

12:45 JST, June 7, 2023

The unseasonal influenza epidemic is continuing. In the seven-day period until May 28, about 5,000 medical institutions across the nation that are designated as fixed observation points for the disease reported 7,975 flu patients. The number is equivalent to 1.62 people per hospital.

The number surpassed one person, which indicates epidemic level, at the end of last year and continued to exceed the level until late May for the first time in 10 years.

A medical expert said, “There were no epidemics [of influenza] for two winter seasons since 2020, when the novel coronavirus crisis began. [The current prolonged epidemic] is caused by people’s immunity levels having been lowered.”

According to an influenza report based on the observation points released June 2 by the Health, Labor and Welfare Ministry, the numbers per hospital in each of the prefectures showed that the highest was 7.07 in Miyazaki Prefecture.

It was followed by Nagasaki Prefecture’s 4.14, Ehime Prefecture’s 3.67 and Niigata Prefecture’s 3.35.

During the weeklong period, a total of 325 kindergartens and elementary, junior high and senior high schools nationwide temporarily closed, or closed classes of specific grades or specific classes.

Although an influenza epidemic continued until late May in 2013 too, this year’s figure is more than double that of the 157 schools and kindergartens that closed that year.

In May this year, there were many group infections in which more than 100 people were infected in each case.

At senior high schools in Oita and Miyazaki cities, nearly 500 people were infected with the flu. Medical experts noted that the flu could have spread through the schools during their sports festivals.

The usual period for a seasonal epidemic of influenza is between December and March.

Regarding this year’s prolonged epidemic, Norio Sugaya, a visiting professor at Keio University who is an expert on infectious disease, said: “Because many people’s immunity levels have fallen, infections tend to spread very quickly. It is also affected by people moving about more than before.”