Colorado Tick Fever: Clinical, Epidemiologic, and Laboratory Aspects of 228 Cases in Colorado in 1973-1974

Abstract

During 1973 and 1974, we looked for cases of Colorado tick fever throughout Colorado; 228 cases were identified. Although 90% of the patients reported exposure to ticks before illness, only 52% were aware of an actual tick bite. Typical symptoms of fever, myalgia, and headache were common, but gastrointestinal symptoms were also prominent in 20% of the patients. Twenty percent were hospitalized; no deaths or permanent sequelae were noted. Persistent viremia (greater than or equal to 4 weeks) was found in about half of the cases; this finding was not associated with the occurrence of prolonged symptoms (greater than or equal to 3 weeks), which were also reported in half of the cases. One patient became reinfected with the virus. Increasing tourism in endemic areas and the frequent occurrence of prolonged or biphasic illnesses provide the potential for patients with Colorado tick fever to seek medical care anywhere in the United States.

The Biological Survey of Canada: A Personal History

“…Symptoms may include fever, chills, headache, back pain, myalgias, generalised weakness, and photophobia with a rash, usually macular or maculopapular, observed in only 5-15% of patients. Approximately half of the cases have recurrence of fever and acute symptoms after an initial period of improvement ("saddleback fever") (Goodpasture et al 1978). Neurological manifestations such as aseptic meningitis and encephalitis have been observed in a small number of infections of children.…”

“…The majority of Colorado tick fever virus cases occur during May to July and over 50% of patients are 20-49 years of age (Goodpasture et al 1978). However, almost a quarter of cases also involve children.…”

Encephalitic Arboviruses: Emergence, Clinical Presentation, and Neuropathogenesis

“…Persons infected with CTFV usually exhibit signs and symptoms within 3 to 6 days of a tick bite [82]. The illness is two staged, with an initial episode of fever, chills, headaches, photophobia, myalgia, malaise, abdominal pain, hepatosplenomegaly, nausea and vomiting, and a rash.…”

“…The second stage is heralded by a high fever with return of symptoms and an increase in their severity with progression to meningitis, meningoencephalitis, or hemorrhagic fever. Children may exhibit the most severe symptoms and require extended hospitalization; death is extremely rare [82].…”

Serologic and molecular diagnosis of Colorado tick fever viral infections.

“…1 It has an abrupt onset with flu-like manifestations and some complications of the disease have been reported, particularly in children. [4][5][6][7] Since the first reports in 1875 to reports of Keiffer and Becker in 1906 and 1926, respectively, 8 on a tick bite-generated biphasic fever having clinical symptoms that does not conform to those of Rocky Mountain spotted fever (RMSF), CTF was recognized as being a separate clinical entity from RMSF. Furthermore, the isolation and characterization of the causative agent, CTF virus, by Florio and others 9 in the 1940s established the viral etiology of the disease.…”