Classification of label-free electrochemical biosensors for detection of pathogens in terms of: target, working electrode, biorecognition element, electrochemical method, limit of detection, and electrochemical probe. Abbreviations: quartz crystal microbalance (QCM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), plaque-forming unit (PFU), colony-forming unit (CFU), indium tin oxide (ITO), carbon nanotube (CNT), magnetic bead (MB), nanoparticle (NP), differential pulse voltammetry (DPV), square wave voltammetry (SWV), anodic stripping voltammetry (ASV), hemagglutination units (HAU), and median tissue culture infectious dose (TCID50).