As the nation’s largest public health service, NYC Health + Hospitals is something of a medical marvel. Its 70 locations — 11 hospitals, as well as other facilities, such as community health clinics, nursing homes and trauma centers — cover New York City’s five boroughs like a fine-mesh safety net. Many of the 1 million patients who visit each year are new to the United States. Some are homeless or incarcerated. These facts continue to amaze Dr. Michael Ambrosino, even after 37 years of working there.