Seventy-three children in New York have been infected with a rare, life-threatening, inflammatory illness potentially linked to the coronavirus  — and a 5-year-old boy in New York City with symptoms of it just died, Gov. Andrew Cuomo said Friday.

State Health Commissioner Dr. Howard Zucker had issued an alert Wednesday to medical providers regarding the “potential association” between “multi-system inflammatory syndrome” — or Kawasaki disease — and COVID-19.

The New York City Health Department earlier this week also issued its own alert about a potential association between Kawasaki disease and COVID-19 after cases emerged in city hospitals.

Kawasaki disease is “similar to toxic-shock-like syndrome, that literally causes inflammation in their blood vessels,” Cuomo said of sufferers. “This past Thursday, a 5-year-old [with symptoms of it] passed away from COVID-related complications, and the state Department of Health is investigating several other cases that present similar circumstances.

“This would be really painful news and would open up an entirely different chapter,” he said.

“This is every parent’s nightmare, right? That your child might be affected by this virus,” Cuomo said during a COVID-19 press briefing in Poughkeepsie.

Cuomo said health experts had believed that while children could be transmitters of the killer bug, they did not become seriously ill from it.

The 5-year-old boy died at Mount Sinai’s Kravis Children’s Hospital Thursday night. A state Health Department official said the child had symptoms of toxic shock syndrome.

“We extend our deepest condolences to the family in the wake of this tragedy. This is an extremely rare and previously unknown presentation of COVID-19 in children. While it is concerning that children are affected, we must emphasize that based on what we know thus far, it appears to be a very rare condition,” said Mount Sinai spokesman Jason Kaplan.

“We encourage any parent who may have concerns to contact their pediatrician for a consultation. Mount Sinai and the health care community will continue to investigate and study this new variant in hopes of finding a solution to this rare condition. In the meantime, we remain mindful that COVID-19 is a highly infectious virus, and encourage everyone to continue to practice social distancing, wear masks and clean hands.”

The city Health Department has identified 20 cases of children under 21 with multi-system inflammatory syndrome, or Kawasaki disease, since April 17. Some of the children also tested positive for COVID or COVID-fighting antibodies.

“The loss of a child is an unfathomable tragedy. With aching hearts, we will continue working with hospitals to ensure that New Yorkers have the information they need to keep their children safe. If a child has symptoms of fever, rash, abdominal pain or vomiting, parents should call their doctor right away,” said city Health Commissioner Dr. Oxiris Barbot.

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Kawasaki disease and multi-inflammatory syndrome are rare childhood illnesses that cause the walls of blood vessels in the body to become inflamed. Kawasaki disease is marked by symptoms including rash and “strawberry tongue” — or a swollen and bumpy tongue — and is a potentially fatal diagnosis.

Symptoms also include a high temperature that lasts for five days or longer, redness in the eyes, rashes and swollen glands in the neck. Children younger than 5 are most at risk.

Treatment includes either aspirin or an infusion of an immune protein called gamma globulin through a vein, which can lower the risk of coronary artery problems, according to the Mayo Clinic. Complications from Kawasaki disease include heart problems such as coronary artery aneurysms.