EPIDEMIOLOGY — R. akari is transmitted to the common house mouse (Mus musculus) by the bloodsucking mite Liponyssoides sanguineus (formerly Allodermanyssus sanguineus). The mouse serves as the reservoir for the disease. L. sanguineus is a small (0.75 to 1.5 mm), colorless arthropod that swells to many times its normal size after a blood meal and becomes bright red in color. L. sanguineus rarely bites humans when mice are plentiful. However, when mouse populations are reduced (eg, by vermin eradication programs), this mite will bite humans and transmit the disease. Although natural infection is thought to occur exclusively by the bite of an infected mite, transmission has occurred in laboratory settings via inhalation of infectious aerosols [2].