Leg pain is also frequently a sign of injury, such as the following: Muscle strain is a common injury that happens when the muscle fibers tear as a result of overstretching. It often occurs in the larger muscles, such as the hamstrings, calves, or quadriceps.
medical Definition of superinfection : a second infection superimposed on an earlier one especially by a different microbial agent of exogenous or endogenous origin that is resistant to the treatment used against the first infection
Terminology. 1  Epitope â The distinct surface features of an antigen, its antigenic determinant. 2  Allergen â A substance capable of causing an allergic reaction. 3  Superantigen â A class of antigens that cause non-specific activation of T-cells, resulting in polyclonal T cell activation and massive cytokine release.