Nicolas Hernandez is accustomed to practicing medicine with limited means.

Hernandez, a doctor at Northwell Health in Plainview, attended Universidad Autonoma de Guadalajara in Mexico.

“I’ve been in a lot of shanty towns [with] minimal resources, sometimes no water. Your basic necessities aren’t there,” said Hernandez, 37. “You rely on what you have. Patients over there are donating their supplies, so you have to be very mindful with what you use.”

Hernandez will report for duty in storm-ravaged Puerto Rico, prepared for dire circumstances. Hernandez, who has family there, will be part of a team of about 70 volunteers from Northwell Health, Montefiore Medical Center in the Bronx, New York-Presbyterian Hospital, Albany Medical Center and Callen-Lorde Community Health Center in Manhattan that expects to leave Thursday. Northwell will provide 27 volunteers, according to its executive vice president and chief operating officer, Mark Solazzo.

The volunteers gathered at the Northwell Health corporate headquarters in New Hyde Park on Wednesday for a briefing on the deployment, which is expected to last between 15 and 17 days.

Mary Mahoney, senior director of emergency management at Northwell Health, who is among those headed to Puerto Rico, said that all but two of the island’s hospitals are now open and nearly half remain on generator power. Most of the island is still without running water, according to officials. The death toll, which on Wednesday rose to 45, is expected to climb with more than 110 people unaccounted for.

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The team of volunteer physicians, nurses, medics, emergency medical technicians and administrators will set up a federal medical station in Ponce or Bayamon, Puerto Rico, and will be equipped to serve “the entire gamut” — from the acutely ill to those with chronic illnesses. The staff is prepared to work with limited power as only about 15 percent of the island has electricity.

“It’s not going to be easy,” Mahoney said.

Stony Brook University Hospital is also working on Puerto Rico relief efforts. It plans to send a 24-person team to help.

Hernandez said he is anticipating the worst, including “not showering for a couple of days,” hot and humid weather and little rest.

“I expect to be on my feet for more than 24 hours at a time,” Hernandez said. “I’ll probably be sleeping in a sleeping bag somewhere. But I know it’s for a greater cause, and for the very limited amount of time that I’m going to be there, it’s nothing compared to what these people are going to have to face in the next couple of weeks to months.”

Hernandez said he and his wife, Nichole, have family on the east and southeast parts of Puerto Rico and in Juncos with whom they have had little contact since the storm hit.

“They have to go to the bigger cities in order to get some type of tower communication,” Hernandez said. “But the information is limited and sometimes we’ll go a couple of days without hearing from them.”

Stacey Berroa, 24, a nurse at Long Island Jewish Medical Center in New Hyde Park, said her family has had a hard time reaching family in Puerto Rico.

“My grandmother was telling me that she was only able to speak to her brothers and sisters once, and they said at the time that they were trying to get away from where a lot of the destruction was,” said Berroa, of Bayside, Queens.

She believes she should be doing more, so she volunteered for the mission.

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“It’s the least I can do, coming from a place of comfort,” Berroa said.

For Hernandez, this mission was a reminder of his calling.

“Northwell has this motto, it’s known as ‘Made for this,’” he said, tears filling his eyes. “And in ways, I feel like I was made for this. I had a really hard time becoming a doctor and now that I am, I’m happy that I can pay back.”