Columbia subject headings:
Typhoid fever--Pennsylvania--Philadelphia--History--19th century.
Water-supply--Pennsylvania--Philadelphia--History--19th century.
Harvard subject headings:
Public health--Pennsylvania--Philadelphia.
Typhoid fever--Pennsylvania--Philadelphia--History--19th century.
Typhoid fever--Pennsylvania--Philadelphia.
Water-supply--Pennsylvania--Philadelphia--History--19th century.
Princeton subject headings:
Public health--Pennsylvania--Philadelphia--History--19th century.
Public health--Political aspects--Pennsylvania--Philadelphia--History--19th century.
Typhoid fever--Pennsylvania--Philadelphia--History--19th century.