The illness, called Pediatric Multi-System Inflammatory Syndrome Associated with COVID-19, prompted an advisory to healthcare providers to immediately report any related symptoms.
County Health Commissioner Dr. Sherlita Amler said officials are still assessing whether underlying conditions were a factor in the death of the child, who was being treated at Maria Fareri Children's Hospital.
Physician-in-Chief Dr. Michael Gewit described it as, "more of an encephalitis picture, brain, neurologic problem that may or may not have been identical to the rest. It was an unusual presentation, and that child did not do well."
There are currently 11 children ranging in age from a few months old to teenagers hospitalized at Maria Fareri with the inflammatory disease.
Meanwhile, Governor Andrew Cuomo announced a 5-year-old boy in New York City had died from COVID-related complications, but it was not immediately clear if the child was also being treated for the inflammatory syndrome.
The boy passed away Thursday night at Mount Sinai Kravis Children's Hospital, which has been treating several children with a similar condition.
"We extend our deepest condolences to the family in the wake of this tragedy," Mount Sinai spokesperson Jason Kaplan said. "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. We encourage any parent who may have concerns to contact their pediatrician for a consultation. Mount Sinai and the healthcare 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."
Cuomo says there are now 73 reported cases of severe illness in children.
In nearly all cases, the children have tested positive for COVID antibodies, meaning they were infected but asymptomatic and only becoming ill four to six weeks after exposure.
"The loss of a child is an unfathomable tragedy," New York City Health Commissioner Dr. Oxiris Barbot said. "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."
The purpose of the health advisory is to inform healthcare providers of the condition, as well as to provide guidance for testing and reporting. Healthcare providers, including hospitals, are required to report to the Department of Health all cases of pediatric multisystem inflammatory syndrome potentially associated with COVID-19 in those under 21 years of age.
"I don't think it's caught anyone off guard," Governor Andrew Cuomo said. "It's developing right now. We are looking at it in New York. The information is all preliminary. We are talking to some hospitals that have some individual cases that they are questioning. But it looks like, again preliminary, young children who either test COVID positive or test for the COVID antibodies which indicate they had the virus, which have an inflammatory response. It's not really respiratory, it's more in the blood vessels themselves, where they have an inflammatory response to the virus itself or to the antibodies."
The possible link has also been reported in the United Kingdom between pediatric COVID-19 and serious inflammatory disease. The inflammatory syndrome has features which overlap with Kawasaki disease and toxic shock syndrome and may occur days to weeks after acute COVID-19 illness.
It can include persistent fever, abdominal symptoms, rash, and even cardiovascular symptoms requiring intensive care.
Health officials say early recognition by pediatricians and referral to a specialist including to critical care is essential, and molecular and serological testing for COVID-19 in children exhibiting the above symptoms is recommended.
The majority of patients have tested positive for COVID-19, some on molecular testing for SARS-COV-2, others on serological testing.
MORE CORONAVIRUS COVID-19 COVERAGE
COVID-19 Help, Information and Resources
Grieving the lost: Tri-State residents who have died
New York state
Share your coronavirus story with Eyewitness News
Stimulus check scams and other coronavirus hoaxes
Coronavirus prevention: how clean are your hands?
Centers for Disease Control and Prevention on coronavirus
Total count of NYC COVID-19 cases based on patient address