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Type B influenza cases surge in children

Published: 18 Apr. 2025, 12:15

A healthcare worker administers a flu vaccine on a patient at a hospital in Guro District, western Seoul, on April 11. [NEWS1]

Korea is grappling with a seasonal surge in type B influenza, with infection rates rising sharply among school-aged children and teens, many of whom are catching the flu again just months after recovering from type A.

A 14-year-old middle school student surnamed Lee recently suffered from type A influenza in January, battling high fever, muscle aches and a sore throat for over a week — so severe that he could barely eat for days.

But just last week, Lee was diagnosed with the flu again — this time, type B. His symptoms, including high fever, were just as intense as before.

“It’s baffling that he caught the flu again just three months later,” said his mother, surnamed Jung, 45.

More children and adolescents like Lee are coming down with type B influenza. The number of suspected flu patients who visited one of the 300 designated sentinel clinics across the country between April 6 and Saturday was 21.6 for every 1,000 outpatients, according to the Korea Disease Control and Prevention Agency (KDCA) on Friday.

That figure marks a 27.8 percent increase from 16.9 the previous week and has risen for five consecutive weeks. It’s also two and a half times the epidemic threshold for this flu season, which is 8.6 for every 1,000 patients.

The flu that is currently going around is type B. About 97 percent of flu virus cases detected last week were type B. In contrast, type A, which was dominant during the winter, has sharply declined.

A hopsital in Daegu is full of flu patients as flu cases surged in recent weeks on Jan. 20. [NEWS1]

Type B influenza is generally considered milder than type A but tends to continue spreading through spring. Even those who already had type A flu this past winter can still get infected with type B.

Typically, flu season peaks in late December to early January, subsides during the winter break, and then resurges in March with the start of the school year, especially among school-aged children and teenagers. The number of patients reported last week was the highest for this period since 2019, when the rate was 42.1 for every 1,000 patients.

This year’s spring flu outbreak is being driven largely by school-aged children and adolescents. Among elementary school students aged seven to 12, the rate of suspected flu cases was 73.3 for 1,000 outpatients, while among those aged 13 to 18, it was 69.9.

The KDCA is urging the public to prevent the flu through frequent hand washing, practicing proper coughing etiquette and wearing masks. Although spring flu usually starts to decline in May, it can sometimes last into the summer.

“The national flu vaccination program for this flu season runs through April 30,” said the KDCA. “If you haven’t received the vaccine yet, it’s still a good idea to get it now.”

Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.

BY RHEE ESTHER [[email protected]]