The number of coronavirus cases in New York state doubled on Friday, hitting 44 — and the majority of them can be traced back to one man, state officials said.

That man — identified by sources as Lawrence Garbuz, 50 — is believed to be the common denominator in at least 37 of the cases — highlighting the alarming way the illness can spread in tight-knit communities.

“We have more investigations to do, but we believe the majority,” of cases came from him, Gov. Cuomo said at a press conference on Friday.

“We’re going down that road for many of these tests,” ­Cuomo added. “He contacted a large number of people, and we are very exhaustive in the testing ­followup.”

Garbuz, who lives in New Rochelle and commuted to work by Metro-North to his boutique law firm in Midtown, became the Empire State’s second case this week.

Since then, his wife, Adina, and two of his children, a 14-year-old girl and 20-year-old man, have tested positive.

As did a neighbor of Garbuz’s who drove him to a hospital in Bronxville on Feb. 27, before Garbuz was transferred to NewYork-Presbyterian/Columbia Hospital in Washington Heights, where he’s in serious condition.

A friend of Garbuz, the friend’s wife and three of their four children also have the bug.

Garbuz, who is still not well enough to interview, likely caught the virus in the Westchester community and not through travel, said Dr. Demetre Daskalakis, the New York City Department of Health’s deputy commissioner.

The Young Israel of New Rochelle synagogue Garbuz attends has been ordered to shut down — and those who attended services, a funeral and bat mitzvah in late February were ordered to self-quarantine at least until March 14.

One Rockland County person who tested positive for the virus was a caterer at either the bat mitzvah or a funeral.

The Frisch School in New Jersey said it would close from Friday until at least Wednesday after 28 students — two from Teaneck and the rest from Westchester County — attended the bat mitzvah at the synagogue and are now under quarantine.

“He attended functions at the temple. He attended a bat mitzvah,” Cuomo said of Garbuz. “There were a large number of people in this gathering.”

“What we’re doing is focusing on, once you have one contact, following that tree, right, to stop people from infecting other people.”

Several of the temple’s congregants have tested positive for the virus, as did the rabbi, Reuven Fink, who was diagnosed Thursday.

Fink teaches two undergraduate classes at Yeshiva University in Washington Heights, which Garbuz’s son attends. The school closed down ­earlier this week.

SAR Academy in Riverdale, the private Jewish school Garbuz’s daughter attends, shuttered on Tuesday.

A 51-year-old Upper West Side man with a “direct nexus” to Garbuz also tested positive, Mayor de Blasio said on Friday, without providing additional details about the ­connection.

His wife and three daughters, ages 8, 10 and 11, are all being tested.

He’s one of five cases in New York City, but the only one with known ties to Garbuz.

The mayor warned New Yorkers to stay home if they had flu symptoms, in light of the virus’ lighting-speed spread.

“Community spread means a greater ease in which this disease can be spread because it’s in so many places,” he said.

“If you do have the symptoms: stay home, don’t go to work, don’t go to school, don’t go to a restaurant, don’t go to the theater.”

Additional reporting by ­Nolan Hicks