Subcutaneous hemorrhaging makes dark areas. Pneumonic plague can spread from person to person independently of animal reservoirs or vectors. Here's a link to a discussion of the recent increase in plague cases in the South Western U.S.A. . Almost all Rickettsia spp. are obligate intracellular parasites. These have been effectively controlled with vaccines.
Vaccines can be very effective.
Before antibiotics, isolation was all one could do. The pathogens which cause these diseases are generally obligate pathogens. These diseases are controlled by individual treatment and public education about safe sex or abstinence. 24 and Lec. Primarily genitourinary tract infection but can spread to eyes, throat etc.