Chlamydia species attack by becoming intracellular; and consuming ATP energy generated by the mitochondria. When ATP energy in the cell is depleted, the pathogen consumes sugar; and the sugar is converted to alcohol via fermentation, creating an environment for fungus to thrive.

Fatigue is a very common symptom in many chronic diseases. As chlamydia spreads from cell-to-cell, the loss of intracellular energy becomes widespread. Fatigue in chronic diseases may occur due to widespread depletion of energy, at the cellular level.