The American Public Health Association (APHA) offers unpaid internships in the Washington DC area.
Summer Internship (June 1-Aug 15). Application deadline is March 1
Fall Internship (Sept 1-Dec 15). Application deadline is July 1
Winter/Spring Internship (Jan 15-May 1). Application deadline is Nov 1
Details about the internships and how to apply are available at: https://www.apha.org/professional-development/apha-internships-and-fellowships