At least four of the hospitalized children under 18 also tested positive for coronavirus, New Jesrey Health Commissioner Judy Persichilli said at Wednesday's briefing.
The 18 affected children are from nine different counties, she said. The newest seven pediatric cases were identified on Wednesday.
Systemic inflammatory response syndrome also has similarities to Kawasaki disease, Persichilli said
"On the Kawasaki front, we'll have more to report as we learn more,'' Gov. Phil Murphy said.
A 4-year-old child was New Jersey's first reported coronavirus death of a person under the age of 18, state officials announced on Friday. The child's name, hometown and other details were not released to protect the privacy of the child and the family, Persichilli said. The child had an underlying medical condition, Murphy added.
New Jersey is among 14 states reporting the pediatric illnesses. New York Gov. Andrew Cuomo made a similar announcement on Wednesday, saying more than 100 children have come down with the inflammatory syndrome in the Empire State.
Children contracting coronavirus is rare. The federal Centers for Disease Control and Prevention (CDC) data suggested last month that children represent only 2 percent of all U.S. cases and their COVID-19 symptoms tend to be milder than those found in adults.
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