Private equity giant Warburg Pincus has acquired a majority stake in CityMD, a growing urgent-care center chain with 68 centers in New York, New Jersey and Washington.

The New York-based firm did not disclose the terms of the deal.

Warburg Pincus said on Tuesday it planned to accelerate CityMD’s growth through strategic acquisitions and by opening additional sites and making it easy for patients to get treatment for minor injuries and ailments that don’t require emergency room care.

CityMD CEO Dr. Richard Park founded CityMD in Manhattan in 2010 with other physicians. It merged with Premier Care in 2013, which hastened its growth.

Urgent-care centers are a hot item among hospitals and providers because they offer a low-cost, convenient alternative to ERs.

“As a category, urgent care centers are still growing because of the overutilization of ERs and because primary care physicians aren’t able to accommodate the influx of patients,” said Dr. Nedal Shami, CityMD’s chief strategy officer.

Tacoma Wash.-based MultiCare Health System, a five-hospital not-for-profit, added 14 urgent-care clinics to the 15 centers it already operated in the Puget Sound area when it bought Immediate Clinic Seattle in September.

Northwell Health, based in New Hyde Park, N.Y., expects to have 45 urgent-care centers open around New York City by year-end, a jump from the 33 it had open at the start of 2017, said Adam Boll, vice president of ventures for the 21-hospital not-for-profit system.

Likewise, HCA Holdings is planning a massive expansion of urgent-care centers and free-standing emergency departments this year as it builds out patient access points in its 14 major markets.

HCA, the nation’s largest investor-owned health system with 169 hospitals, expects to increase urgent-care locations from 72 today to 120 by year-end.

Warburg Pincus is one of the nation’s largest private equity firms with $44 billion in assets.