[8] The precise incidence of the disease is unknown, as diagnostic facilities are not available in much of its large native range, which spans vast regions of equatorial jungle to the subtropics.

In rural Thailand and Laos, murine and scrub typhus account for around a quarter of all adults presenting to hospital with fever and negative blood cultures.

[9][10] The incidence in Japan has fallen over the past few decades, probably due to land development driving decreasing exposure, and many prefectures report fewer than 50 cases per year.

[11][12] It affects females more than males in Korea, but not in Japan,[13] which may be because sex-differentiated cultural roles have women tending garden plots more often, thus being exposed to vegetation inhabited by chiggers.

However, overshadowing of the diagnosis is quite often as the clinical symptoms overlap with other infectious diseases such as dengue fever, paratyphoid, and pyrexia of unknown origin (PUO).

Usually, scrub typhus is often labelled as PUO in remote endemic areas, since blood culture is often negative, yet it can be treated effectively with chloramphenicol.

[20] Other methods include culture and polymerase chain reaction, but these are not routinely available[21] and the results do not always correlate with serological testing,[22][23][24] and are affected by prior antibiotic treatment.

[38] The first known batch of scrub typhus vaccine actually used to inoculate human subjects was dispatched to India for use by Allied Land Forces, South-East Asia Command in June 1945.

An attempt to verify the efficacy of the vaccine by using a placebo group for comparison was vetoed by the military commanders, who objected to the experiment.

[43] Dora Lush, an Australian bacteriologist, died after accidentally pricking her finger with a needle containing scrub typhus while inoculating a mouse in an attempt to develop a vaccine.

[45] Several members of the U.S. Army's 5307th Composite Unit (Merrill's Marauders) died of the disease, as well as many soldiers in the Burma theatre;[46] and before 1944, no effective antibiotics or vaccines were available.

In the chapter entitled "The Green War", General MacArthur's biographer William Manchester identifies that the disease was one of a number of debilitating afflictions affecting both sides on New Guinea[49] in the running bloody Kokoda battles over extremely harsh terrains under intense hardships— fought during a six-month span[50] all along the Kokoda Track in 1942–43, and mentions that to be hospital-evacuated, Allied soldiers (who cycled forces) had to run a fever of 102 °F (39 °C), and that sickness casualties outnumbered weapons-inflicted casualties 5:1.

Where the Allies had bases, they could remove and cut back vegetation, or use DDT as a prophylaxis area barrier treatment, so mite- and tick-induced sickness rates in forces off the front lines were diminished.