A 17-year-old student died Wednesday from acute pneumonia possibly caused by coronavirus, which would make him the first teenager in Korea to die of the infection.

The sudden death of the boy, who had no prior history of illness, just six days after being hospitalized has left medical experts stumped.

Korea Centers for Disease Control and Prevention chief Jung Eun-kyeong told reporters, "The patient repeatedly tested negative for coronavirus and only the last test came out partially positive, prompting the KCDC to handle the testing."

According to hospital officials, the teenager was tested eight times from March 13 until this Wednesday and only the last test suggested some probability of infection.

He first visited a local hospital on March 12 after displaying symptoms of pneumonia, but a doctor sent him back home. His condition worsened the next day and the teenager developed a high fever, prompting his parents to take him to the bigger Yeungnam University Medical Center where he was treated under quarantine. He was placed on a respirator on March 14.

