DR.An Na has just returned to Beijing from a medical assistance program in Pakistan,and her warm smile and passion are infectious at first sight.An,a Chinese gynecologist,began working with her program,which is affiliated with Médecins Sans Frontières (MSF - also called Doctors Without Borders) in Sierra Leone in 2011.But she is not the only Chinese physician working with the international medical and humanitarian non-governmental organization (NGO).In recent years,an increasing number of Chinese doctors have partnered with MSF to provide medical aid to the world's most in need.