Surge in Type B Flu Cases... Rising for 5 Weeks, Especially Among Children and Adolescents

21.6 Suspected Flu Cases per 1,000 Outpatients... Up 28% from Previous Week
Type B Flu Causes Milder Symptoms Than Type A,
But Outbreak May Continue Throughout Spring

Influenza (flu) continues to spread, particularly among children and adolescents, during the spring season.

On September 20 last year, when free influenza (flu) vaccination began ahead of winter, a notice for free vaccination was posted at an otolaryngology clinic in Seoul. Photo by Kang Jinhyung aymsdream@

According to the Korea Disease Control and Prevention Agency on April 18, during the 15th week of this year (April 6?12), 21.6 out of every 1,000 outpatients who visited 300 sample surveillance clinics nationwide were suspected flu cases.

This represents a 27.8% increase compared to 16.9 cases per 1,000 outpatients a week earlier, marking a rise for the fifth consecutive week. The current figure is also 2.5 times higher than the seasonal epidemic threshold of 8.6 cases per 1,000 outpatients.

Typically, flu outbreaks peak between late December and early January, then subside before resurging among students as the new school year begins in March. In terms of patient numbers for the 15th week, this year has seen the highest level since 2019, when there were 42.1 cases per 1,000 outpatients, making it the largest in six years.

This spring’s flu outbreak is also being driven by the student age group. Among children aged 7?12, the elementary school age group, there were 73.3 suspected flu cases per 1,000 outpatients, while among adolescents aged 13?18, the figure soared to 69.9 per 1,000 outpatients.

Last week, about 97% of the influenza viruses detected were type B. While type B typically causes milder symptoms than type A, it tends to circulate through the spring. Even those who contracted and recovered from type A flu last winter can become infected with type B flu.

The agency emphasized the importance of handwashing, practicing proper cough etiquette, and wearing masks to prevent flu infection. It also advised that, since the national flu vaccination program for this season runs until April 30, anyone who has not yet been vaccinated should do so as soon as possible.