Why do the symptoms of certain viral infections occur after having disappeared for a period of time?

Http://www.virology.ws/2014/10/08/the-incubation-period-of-a-viral-infection/

Glucose, also called grape sugar, blood sugar or corn sugar, is among the simplest and one of the primary naturally occurring sugars. produced naturally by plants as the primary photosynthesis product, it is heavily used by living beings as a main energy source and is necessary for cellular respiration. chemically, it is a monosaccharide carbohydrate and serves as a building block for complex sugars like starch.

Both prokaryotic and eukaryotic cells have ribosomes and cell membranes