obtaining biological data containing at least an expression level of MX dynamin-like GTPase 1 (MX1) and an expression level of C-reactive protein (CRP) in the blood of a subject;

calculating by a hardware processor a distance between a segment of a curved line and an axis defined by a direction, said distance being calculated perpendicularly to said axis, between a point on said axis and a corresponding point over said curved line, said points being defined by a coordinate δ along said direction, wherein said coordinate δ, once calculated, equals a₀+a₁X+a₂Z_MX1, and wherein said X is a value of said CRP in μg/ml, and said Z_MX1 is a z-score of said MX1 relative to a group of subjects previously diagnosed with a bacterial infection;

storing said distance in a memory;

by said hardware processor, correlating said distance to the presence of, absence of, or likelihood that the subject has, a bacterial infection;

generating on a graphical user interface an output of said presence, absence or likelihood;

obtaining said likelihood based on said distance;

comparing said likelihood to a predetermined threshold; and

treating the subject for said bacterial infection with an antibiotic agent when said likelihood is above said predetermined threshold;

wherein at least 90% of said segment is between a lower bound line f(δ)−ε₀ and an upper bound line f(δ)+ε₁, wherein said f(δ) equals 1/(1+exp (−δ)), wherein each of said ε₀ and said ε₁ is less than 0.5, and wherein a₀ is from about −2.4 to about −1.9, a₁ is from about 0.04 to about 0.05, and a₂ is from about −0.39 to about −0.43.