The fight against the coronavirus in the U.S. reached a heartbreaking milestone this weekend as Illinois Gov. J.B. Pritzker announced the death of an infant in his state believed to be caused by COVID-19.

“I know how difficult this news can be, especially about this very young child. Upon hearing it, I admit, I was immediately shaken, and it’s appropriate for any of us to grieve today,” Pritzker, a father of two, said at a news conference Saturday.

Illinois Department of Public Health Director Dr. Ngozi Ezike also spoke, telling reporters, “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.”

Officials have not said how old this baby was or what their health was like before contracting COVID-19 but we do know that the youngest baby to die in China did have a preexisting condition.

Still, health officials are asking parents of children without pre-existing conditions to take the recommendations on physical distancing seriously.

While preliminary research suggests that children with COVID-19 usually don’t get as sick as adults, the youngest age groups—infants and preschoolers—see more severe cases than older kids do. According to a new study posted online pre-publication by the journal Pediatrics, babies and preschoolers can become severely ill if they get COVID-19, and this case in Illinois certainly proves it.

At the presser in Illinois, Dr. Ezike asked everyone, parents and non-parents alike, to follow the recommendations and stay home.

“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, Ezike said.