Epidemiological markers are biological markers used to characterize and discriminate between microorganisms based on genetic variation. They can be phenotypic markers that identify observable traits, or genetic markers that identify DNA sequence variants. Epidemiological markers are mostly used for strain typing to classify isolates, catalogue genetic variation, and confirm or identify disease outbreaks for epidemiological purposes. They allow discrimination between related and unrelated strains in a stable, widely available, and easily detectable way.