The organism is found in the Western Hemisphere and is transmitted via the bite of hard ticks of the genus Amblyomma.

[6] Other confirmed or probable human cases have been reported to have acquired infection elsewhere in the United States (e.g., Arizona, Georgia, and Mississippi), as well as in Argentina, Brazil, Colombia, Mexico, and Uruguay.

[8] In the United States, most of the 40 cases reported to the Centers for Disease Control and Prevention (CDC) as of 2016 became infected between the months of July and September.

[13]: 27  In addition, indirect immunofluorescence antibody (IFA) assays using paired acute and convalescent sera can be used.

"[8] In 1939, Ralph R. Parker, director of the Rocky Mountain Laboratory, and others published a paper on "a rickettsia-like infectious agent.

"[7][14] The agent, found in Amblyomma maculatum ticks collected from cows in Texas, produced mild disease in guinea pigs.