I found a good article which discusses the effects of stress on the body including the immune response. It is critical to control stress particularly for those with chronic infections. Western Medicine has long held views that there is a single cause, single effect but recent research is beginning to see the delicate relationships in the human body. Cortisol is one of many hormones that is excreted under stress, however chronic stress releases more coritsol which begins to have a bad effect in the body, the immune response is covered in this article.
Here is the article : https://www.sciencedaily.com/releases/2012/04/120402162546.htm