Outbreak of Exanthematous Illness Associated with Zika, Chikungunya, and Dengue Viruses, Salvador, Brazil

Abstract

treated with doxycycline (100 mg 2×/d) for 10 days; they clinically recovered, and laboratory abnormalities returned to reference ranges at discharge 12 days after admission.The remaining 22 persons did not report any malaise and were examined 1 month after tick bite.They appeared healthy at that time, and PCR and ELISA gave negative results, arguing against possible asymptomatic B. miyamotoi infection.We estimated the probability of B. miyamotoi transmission to humans to be 8.3% (95% CI 4%-18% using a Bayesian approach [8] or 95% CI 0%-21% using an SPSS bootstrapping procedure [SPSS Inc., Chicago, IL, USA]).For comparison, among 68 persons bitten by B. burgdorferi sensu lato-infected ticks in the Netherlands, erythema migrans developed in 4.4% (95% C.I. 2.1%-8.3%)persons; 3 (4.4%)others seroconverted without clinical symptoms ( 9).This pilot study has several limitations.We did not follow up persons bitten by B. burgdorferi sensu lato-or TBEV-infected ticks because they received either antimicrobial drugs or anti-TBE immunoglobulin as a preventive measure.Because of labor constrains, we did not study persons bitten by "PCR-uninfected" ticks; however, they were not hospitalized at RHID, the only hospital in the region for patients with evident tick-borne diseases.We did not use any serologic techniques specific for relapsing fever Borreli (e.g., GlpQ ELISA).Although we did not test for Rickettsia or Babesia spp., we did not find TBEV RNA, B. burgdorferi sensu lato 16S RNA, pathogenic Ehrlichia 16S RNA, or pathogenic Anaplasma DNA in the 2 B. miyamotoi-positive patients' blood samples.We demonstrated that the transmission rate of B. miyamotoi appears to be equal to, or higher, than that of B. burgdorferi sensu lato (1,9,10).Our data indicate that, annually, clinical B. miyamotoi infection might develop in at least 0.005% of persons living in regions to which Ixodes spp.ticks and B. miyamotoi are endemic.This estimate corresponds to ≈33 cases annually in Izhevsk, which is similar to the previously published results of hospital-based surveillance for B. miyamotoi (3,6).