Borrelia species fall into two groups, the Borrelia burgdorferi sensu lato (Bbsl) complex, the cause of Lyme borreliosis (also known as Lyme disease), and the relapsing fever group. Both groups exhibit inter- and intraspecies diversity and thus have variations in both clinical presentation and diagnostic approaches. A further layer of complexity is derived from the fact that ticks may carry multiple infectious agents and are able to transmit them to the host during blood feeding, with potential overlapping clinical manifestations. Besides this, pathogens like Borrelia have developed strategies to evade the host immune system, which allows them to persist within the host, including humans. Diagnostics can be applied at different times during the clinical course and utilize sample types, each with their own advantages and limitations. These differing methods should always be considered in conjunction with potential exposure and compatible clinical features. Throughout this review, we aim to explore different approaches providing the reader with an overview of methods appropriate for various situations. This review will cover human pathogenic members of Bbsl and relapsing fever borreliae, including newly recognized Borrelia miyamotoi spirochetes.

Biology Centre CAS Institute of Parasitology Ceske Budejovice Czech Republic

Department of Infection and Immunity Luxembourg Institute of Health Esch sur Alzette Luxembourg

Department of Microbiology National Center of Infectious and Parasitic Diseases Sofia Bulgaria

National Institute for Agrarian and Veterinarian Research Lisboa Portugal

School of Health Sport and Bioscience University of East London London United Kingdom

Scientific Veterinary Institute Novi Sad Rumenacki put 20 Novi Sad Serbia

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