RESUMEN
BACKGROUND: Fever of unknown origin (FUO) is one of the greatest challenges for clinicians and patients. There are more than 200 etiological agents of FUO, among these the most common is the role of infection, neoplasms, and diseases of connective tissue. The aim of the present study is to investigate the role of the infectious agents parvovirus B19 (B19V) and Coxiella burnetii (C. burnetii) in the development of fever of unknown origin by a set of immunoenzymatic and molecular methods. METHODS: The present study included a total of 70 adult patients diagnosed with FUO and hospitalized in Bulgarian Hospitals. A control group of 26 healthy people were also included. Serological (indirect enzyme immunoassay test for detection of B19V and C. burnetii Ph. II specific IgM/IgG) and molecular (extraction and detection of infectious nucleic acids) methods were used. RESULTS: From all patients with FUO, a positive result for B19V-IgM was obtained in 18/70 (25.71%, 95% CI: 15.47 - 35.95) and the highest percentage was found in age groups 0 - 9 and 10 - 19 years. Protective B19V immunity and past viral infection was reported in 41/70 (58.57%, 95% CI: 47.03 - 70.11), and this percentage corresponded with the control group 16/26 (61.54%, 95% CI: 42.84 - 80.24). Anti-C. burnetii Ph. II-IgM was demonstrated in 13/70 (18.57%, 95% CI: 9.46 - 27.68). A relatively high percentage of affected patients were ≤ 40 years. Anti-C. burnetii Ph. II-IgG was detected in 24/70 (34.29%, 95% CI: 23.17 - 45.41). The control group has a 100% negative result for acute B19V and C. burnetii infection. A positive B19V-DNA result was obtained in 12/70 (17.14%, 95% CI: 8.31 - 25.97) patients. In 11/12 (91.67%) it was in combination with positive B19V-IgM marker. Of the total 70 sera tested, a positive PCR results for C. burnetii-DNA were obtained in 11 (15.71%, 95% CI: 7.18 - 24.24). According to clinical manifestation and concomitant symptoms, a high percentage of B19V and C. burnetii positives were associated with FUO and fever, headache, chills, and rash. CONCLUSIONS: It is of particular importance for a correct diagnosis of FUO to use a combined laboratory approach to prove acute or persistent infection and to test for a set of etiological agents.
