Now, they are on their first mission in the United States -- helping victims of Hurricane Sandy, the megastorm that destroyed much of New York's metropolitan area.
By last Saturday (10 November), medical teams were on the ground in the Rockaways, a hard-hit section of Queens, as well as Staten Island, New Jersey and Brooklyn.
The doctors, nurses and medical students provide free medical evaluations to residents still without power and help them fill and pick up prescriptions they might otherwise go without.
While noting the environment was "apples and oranges" compared with many of the locations Doctors Without Borders has worked, media relations manager Michael Goldfarb said there were gaps in health care after the storm that the organisation could address.
"There are real needs here and we're doing our best to try to meet them," he said. "There are vulnerable people here."
There are National Guard trucks on the streets, and litter left behind where floodwaters receded.
Gas rationing in New York City began Friday (9 November), with drivers only able to fill up on even or odd days depending on the number at the end of their license plate.
At abandoned gas stations, cones and caution tape alerted motorists that they should move on.
Candice Humphrey, 28, lives in Brooklyn and never thought the first place she would work with Doctors Without Borders would be her own backyard.
A nurse, who started training with the organisation in September, Humphrey is awaiting her first placement overseas.
In Queens, she has provided home-visit health care to residents in buildings such as one apartment complex that had no electricity and no running water above the fifth floor.
Some residents on upper floors "are essentially trapped," she said, particularly the elderly, and those with knee or back problems that make it impossible for them to walk up and down stairs.
"We are seeing a lot of people who are running out of their medicines," Humphrey said. "People with diabetes, HIV, high cholesterol, other chronic health conditions are not getting the medications that they normally take because the supply chain is broken."
Shauvan Nichols stopped by with her 9-year-old niece, Soraya, hoping to pick up medications for her elderly mother, who has diabetes and lives on the 15th floor of Nichols' building across the street.
The power is still out, and her mother can't go up and down all those stairs.
"For people like them, it's good, because they're not walking around," Nichols said. "I think it's really good that the guys came over here just to help them."
Nikole Russell, 64, lives in the building where the clinic is set up and has been helping direct friends and neighbors to it. She praised volunteers she'd seen walk up 20 flights of stairs -- more than once --to tend to patients on that floor.
"Doctors Without Borders, Red Cross, we love you, we thank you, we appreciate what you have done for all the tenants," Russell said. "And what you're about to do, because you've got to come back tomorrow, too."