The first infant death related to COVID-19 in the United States has been reported in the Chicago area today (March 28).

"There has never before been a death associated with COVID-19 in an infant," said Dr. Ngozi Ezike, the director of the Illinois Department of Public Health (IDPH). "A full investigation is underway to determine the cause of death. 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."

The age of the infant, who lived in Cook County, has not been released. This isn't the first death in an infant confirmed to have COVID-19. In China, a 10-month-old with the disease, died 4 weeks after being admitted to the Wuhan Children's Hospital, according to a March 18 report published in the New England Journal of Medicine .

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Though as the pandemic unfolds, doctors are realizing that no age group is immune to the virus nor to its severe health effects, the disease caused by the novel coronavirus still appears to be more severe in older adults.

More than 85% of COVID-19 deaths in Illinois have been in patients aged 60 and older. And across the U.S., even though 31% of confirmed COVID-19 cases occurred in adults ages 65 and older, this age group represents 45% of hospitalizations, 53% of admissions to the ICU and 80% of the deaths, according to the Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report on March 26.

Currently, Illinois has confirmed 3,491 COVID-19 cases and 47 related deaths in 43 counties. The ages of those infected, range from younger than 1 to 99 years, the IDPH reported.

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Editor's note: This article was updated to fix the spelling of Cook County.

Originally published on Live Science .