This spring without the mask-wearing mandate in three years, Korea is witnessing a quick increase in the number of respiratory diseases including flu, especially among young children and infants.

According to data by the Korea Disease Control and Prevention Agency (KDCA), 13,268 local patients were hospitalized at 220 sampled medical institutions for viral acute respiratory infections and flu during the seven-week period from the 10th week in March to the 16th week in April. 

The figure is more than 13 times the number of patients hospitalized for the same reason a year earlier (12,000).

The KDCA data also showed that 19.9 out of 1,000 Korean outpatients visiting 196 sampled medical institutions across the country demonstrated suspected symptoms of influenza during the April 16-22 week.

The weekly proportion of such flu patients has been on the rise for five consecutive weeks.

Last week, 267 patients were hospitalized for flu, up 38 percent from the previous week. 

The number of hospitalized patients who suffered from viral acute respiratory infections -- including adenovirus, rhinovirus, and respiratory syncytial virus (RSV) -- also went up to 2,335 in the April 16-22 week from 2,311 in the previous week. 

Respiratory diseases were once fading in the wake of Covid-19 because people increasingly wore masks, kept hand-washing and other precautions, and traveled less. 

However, with the gradual easing of social distancing rules, respiratory diseases started to pick up in the last winter. 

The number of patients with respiratory diseases is returning to the level before the pandemic. 

Health officials said that most of the patients hospitalized for flu,  adenovirus, and rhinovirus were young children aged between zero and six.