NEW YORK CITY — One hundred New York City children have the potentially fatally syndrome that may be linked to new coronavirus, Mayor Bill de Blasio announced Thursday.

The numbers of pediatric multi-system inflammatory syndrome spiked this week as New York City became grimly aware children were not as safe from the virus as health experts first believed.

“This is really troubling to see now after we thought we saw a consistent pattern, something new has been happening,” de Blasio said. “The number of children infected continues to grow.”

Fifty-five of those children have tested positive for COVID-19 or its antibodies and a five-year-old boy has died from the syndrome, de Blasio said.

“Call your doctor immediately,” de Blasio told parents of children exhibiting symptoms. “With early detection, we can save the lives of these children.”

Read the City’s PMIS fact sheet here.

New York State has 110 cases and three fatalities: the New York City 5-year-old, a 7-year-old from Westchester, and an 18-year-old girl from Long Island, Gov. Cuomo said Thursday.

The state’s health department created criteria to help healthcare professionals diagnose, track and report incoming cases, Cuomo said.

“Now maybe children are affected and maybe we didn’t know it,” said Cuomo. “Do not underestimate this virus, it has beaten us at every turn and it has surprised us at every turn.”