If the scenario ends without the effect having been removed, the Disease carries over into every future scenario (any scenario, not just exploration).
Each Disease has a Stat Track and a number listed next to it in parentheses. Diseases reduce the base value of the listed Stat Track by the value provided. For instance, a Disease (Mind 1) will reduce base Mind values by 1 for anyone afflicted with the Disease. Unlike with most effects, these can reduce a Stat Track's base value up to -4.
Diseases should be applied last when computing Stat Track base values. For instance, if a PC has -1 Skill from their Background, -1 Skill from their Craft, -1 Skill from equipped Gear, and -1 Skill from a Disease, the final base Skill should be -3. The first three -1 penalties are applied first; however, the third is ignored because -2 is the usual minimum base value. After this, the -1 from the Disease is applied, bypassing the normal limit and resulting in a -3 base Skill value.
Any additional, unique consequences of the disease are listed in the Special entry of the imposing Action (or as a part of the Disease text if from some other effect). If the Special entry contains multiple effects, only effects listed as lasting until the end of the scenario are considered to be part of the Disease. Any remaining parts of the Special entry do not persist into future scenarios along with the Disease.
PCs can heal from a Disease in a place where such healing is provided (usually a town of sufficient size or similar locale). This usually costs 1 Valuable and further requires performing a rest. Healing is also possible from certain effects (often from Gear and powerful cards), and the DM may provide additional alternatives. If a Disease can be applied multiple times (such as cumulative damage), all instances of that Disease can be removed from a PC as though it were one instance, even if the cumulative effects were imposed by more than one source.