Tickborne relapsing fever - United States, 1990-2011

Abstract

Tickborne relapsing fever (TBRF) is a zoonosis caused by spirochetes of the genus Borrelia and transmitted to humans by ticks of the genus Ornithodoros. TBRF is endemic in the western United States, predominately in mountainous regions. Clinical illness is characterized by recurrent bouts of fever, headache, and malaise. Although TBRF is usually a mild illness, severe sequelae and death can occur. This report summarizes the epidemiology of 504 TBRF cases reported from 12 western states during 1990-2011. Cases occurred most commonly among males and among persons aged 10‒14 and 40‒44 years. Most reported infections occurred among nonresident visitors to areas where TBRF is endemic. Clinicians and public health practitioners need to be familiar with current epidemiology and features of TBRF to adequately diagnose and treat patients and recognize that any TBRF case might indicate an ongoing source of potential exposure that needs to be investigated and eliminated.

FIGURE

Number of reported cases of tickborne relapsing fever — United States, 1990–2011* * One dot was placed randomly in the county of exposure where known. Clinicians can contact county or state health departments to learn whether tickborne relapsing fever has been reported in a particular county. Shading indicates those states where tickborne relapsing fever was reportable. No cases were reported from North Dakota.