NEW YORK (CBSNewYork) – New York City now has 100 cases of pediatric multi-system inflammatory syndrome, a rare illness believed to be linked to COVID-19.

That number rose from 82 on Wednesday, and 52 a day before. Of the 100 cases, 55 tested positive for the coronavirus or its antibodies.

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“This is a deep concern, and we’re going to throw everything we’ve got at it,” Mayor Bill de Blasio said during Thursday’s briefing.

WATCH: Mayor De Blasio’s Daily Coronavirus Briefing 

On Wednesday, Gov. Andrew Cuomo said there were 102 cases under investigation statewide and three deaths, including a 5-year-old boy from the Bronx.

Parents should be on the lookout for symptoms, including persistent fever, rash, abdominal pain or vomiting. The mayor said early detection is key, and anyone who needs a doctor can call 311.

CORONAVIRUS PANDEMIC

De Blasio also said the city is expanding the criteria for testing at its 23 walk-in public health and hospital sites.

They’re now open to:

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  • Anyone experiencing symptoms, including cough, fever, shortness of breath or loss of test or smell
  • Anyone with close contact to a confirmed case, including housemates and intimate partners
  • Anyone who works in a nursing home, shelter or adult care facility

Call 311 or visit nyc.gov/covidtest for an appointment and testing site near you.

CORONAVIRUS: NY Health Dept. | NY Call 1-(888)-364-3065 | NYC Health Dept. | NYC Call 311, Text COVID to 692692 | NJ COVID-19 Info Hub | NJ Call 1-(800)-222-1222 or 211, Text NJCOVID to 898211 | CT Health Dept. | CT Call 211 | Centers for Disease Control and Prevention

The mayor shared an update on the city’s homeless outreach while subways are shut down for overnight cleaning.

He said of the 824 people who accepted help – either into a shelter or hospital – in the first week, 103 of them remain there.

“The fact that 103 have stayed in so far, is a huge step in the right direction,” he said. “So we’ve got to break the vicious cycle that held people in a life that was truly dangerous and unhealthy and not anything we want to see a human being live in. This is a very promising sign.”

De Blasio said the latest indicators showed “a very good day, and you deserve the credit.”

Hospitalizations decreased from 78 on May 11 to 59, the number of patients in the ICU dropped from 561 to 517 and the percentage of people testing positive dipped from 13 to 11%.

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“Three for three – a perfect day, New York City,” he said. “So let’s now put together a bunch of them, and that’s what’s going to help us take the next big step forward.”