25% to 30% Rocky mountain spotted fever is an infection transmitted by ticks. Before the use of antibiotic therapy, the death rate was about 25% to 30%. Nowadays, with treatment, the death rate is about 4%. Despite the disease being first recognized and described in the rocky mountain region, 95% of U.S. Cases are in the eastern U.S. (>50% of cases are in the southern coastal atlantic states).
Difficult to know. It is difficult to know because if you know someone is infected, they are treated.