Test code links throughout this Guide refer to the corresponding test in the User's Guide. A characteristic feature of the rickettsiae is that they multiply in an arthropod as part of their life cycle. The incubation period for most rickettsioses ranges from 3 to 14 days.
Most patients develop nonspecific symptoms and signs.
Onset of disease is sudden in about half of the cases. Fever and headache are the most commonly reported symptoms, but chills, myalgias, arthralgias, malaise, and anorexia also are noted. Rash is a hallmark of infection, but it usually follows systemic symptoms and its absence should not rule out a possible rickettsial etiology. Serious central nervous system impairment can also be seen with typhus. IFA is one of the most sensitive serologic tools for confirming diagnosis.