Initially, "doctors relied on two theories about yellow fever: One camp believed it was mysteriously spread by filthy conditions much like cholera and dysentery. Terms like fomites, effluvia, and noxious gasses peppered medical literature in an attempt to explain what substance - whether animal matter, fungal, or gaseous - spread the disease. The other side held that the fever was imported each summer into the city by railroads and river traffic."1

"Ships were forced to spend weeks anchored outside of a city until the crew showed no signs of disease among them. Vessels and their cargo were initially intended to spend thirty days - trentina - in the harbor, but that later changed to forty days - quarantina . In America, trains and paddleboats could also be quarantined to prevent smallpox, plague, and fevers."1

Adding to the complexity, there was not a single central public health service in existence at that time. There were two agencies vying for the lead role in American health policy: the American Public Health Association and the Marine Hospital Service. Researchers not only had to contend with the unknowns of developing cures and treatments for the epidemic, but the power struggle at play between these two institutions.