An interstate outbreak of tick-borne relapsing fever among vacationers at a Rocky Mountain cabin

In July 1995, an outbreak of acute febrile illness affected 11 (48%) of 23 family members from Nebraska and Kansas who had vacationed at a Colorado cabin in June. Similar symptoms were identified among five (17%) of 30 additional persons from Nebraska, Kansas, Florida, and Texas who had vacationed at the same cabin. Symptoms suggested tick-borne relapsing fever (TBRF). Although no spirochetes were detected in available blood smears from five case-patients, Borrelia hermsii was cultured from the blood of one case-patient and two chipmunks trapped near the cabin. Case-patients were more likely than non-ill cabin visitors to have slept on the floor (odds ratio [OR] = 28.0, 95% confidence interval [CI] = 3.0-258) or in the top bunk bed (OR = 5.2, 95% CI = 1.1-25.1). Tick-borne relapsing fever should considered in the differential diagnosis of fever in patients who have stayed overnight in mountain cabins in the western United States.