In stochastic processes, chaos theory and time series analysis, detrended fluctuation analysis (DFA) is a method for determining the statistical self-affinity of a signal.
Sore throats caused by tonsillitis or streptococcus may trigger a canker sore even after the initial throat condition has subsided. Also known as an aphthous ulcer, canker sores are painful and unsightly, but they are not contagious.
Canker sores don't involve the herpes virus and aren't contagious. No one knows what causes them. Cold sores generally herald their arrival with a warning period of red, irritated skin. Blisters form, rupture, and then crust over before healing.