A student at an elementary school in Siheung, Gyeonggi Province, was confirmed to be infected with norovirus on Wednesday.
Siheung Public Health Center said Wednesday that health authorities had launched an epidemiological probe last week after some 50 students at an elementary school showed signs of food poisoning.
Since Friday, 52 students have been absent or left school early due to stomach pain and diarrhea.
One student tested positive for norovirus, according to the regional institute for health and environment, which is examining biological samples from the affected students. Authorities expect the number of infected to grow as sample tests continue.
Those confirmed or suspected to be infected with norovirus are suspended from school or work for at least 48 hours after the symptoms disappear.
Authorities are looking into the cause of the infection.
Norovirus is a common cause of food poisoning, especially in the winter months. The highly contagious virus usually spreads through contaminated food and water. It causes vomiting, stomachache and diarrhea within 24 to 48 hours of infection.
By Choi Ji-won (email@example.com)