The first death of a U.S. infant linked to the coronavirus pandemic after the disease claimed the life of a child younger than a year old in Illinois, officials in the state of Illinois said on Saturday, marking an extremely rare case of juvenile death in the global pandemic.

The Illinois Department of Public Health (IDPH) reported an infant died in Chicago was younger than one year and had tested positive for coronavirus (COVID-19) disease.

“There has never before been a death associated with COVID-19 in an infant. A full investigation is underway to determine the cause of death,” IDPH Director Dr. Ngozi Ezike said in a statement. “We must do everything we can to prevent the spread of this deadly virus. If not to protect ourselves, but to protect those around us.”

“Severe forms with the young are very rare,” Salomon noted. In the US state of California last week, the Los Angeles County Department of Public Health said that a teenager had tested positive for COVID-19 and died.

Kids have made up a small fraction of cases of coronavirus worldwide. A letter published earlier this month in the New England Journal of Medicine by Chinese researchers confirmed the death of a 10-month-old man with COVID-19. The baby had an intestinal blockage and an organ failure, and died four weeks after being hospitalized.