Walter Reed was a U.S. Army physician who in 1901 led the team that confirmed the theory of Cuban doctor Carlos Finlay that yellow fever is transmitted by a particular mosquito species rather than by direct contact. This insight gave impetus to the new fields of epidemiology and biomedicine, and most immediately allowed the resumption and completion of work on the Panama Canal (1904–1914) by the United States. Reed followed work started by Finlay and directed by George Miller Sternberg, who has been called the "first U.S. bacteriologist".