In the medical world, there are phases in the development of a disease.  In the same way, there are phases of destruction in a spiritually healthy person.  

The physical defilement stages are:

• Ignorance of “preventive” measures to avoid contamination.
• Exposure to one who is already “infected.”
• Contamination (defilement) by allowing the “germs” to enter our system.
• Onset of an infection as the “germs” overcomes our normal defenses.
• Disease when the infection destroys vital life-support functions.

Along the same lines, the spiritual defilement stages of a spiritual healthy person are:

Ignorance
Satan will gain an advantage over us if we are ignorant of his devices.  Ignorance is not being aware of the destructive power of untrue or distorted words. 
“The tongue is a fire, a world of iniquity…it defileth the whole body, and setteth on fire the course of nature; and it is set on fire of hell.” ~James 3:6
“Death and life are in the power of the tongue.” ~Proverbs 18:21

Exposure
Exposure is entering into conversation with a person who is a carrier of an evil report.
"A prudent man forseeth the evil, and hideth himself; but the simple pass on and are punished.” ~Proverbs 27:12 

Defilement
Defilement is receiving an evil report from another person and believing that it is true.
"The words of a talebearer are as wounds, and they go down into the innermost parts of the belly.” ~Proverbs 26:22 

Infection
The onset of infection comes from responding to an evil report with human reasoning and emotion rather than with the spiritual. 
“The simple believeth every word; but the prudent man looketh well to his going.” ~Proverbs 14:15  “As coals are to burning coals and wood to fire; so is a contentious man to kindle strife.” ~Proverbs 26:21

Disease
Having the disease is being mentally and emotionally controlled by the evil report and by the destructive spirit of the one who gave it to you.