With health anxiety, we have unhelpful or inaccurate core beliefs about health and illness. These beliefs lead us to process information in a biased way. We tend to seek out "evidence" of our belief (e.g. that serious disease is everywhere) and we ignore or dismiss evidence to the contrary. It can be helpful to use a CBT technique and track your thoughts and assumptions in a thought record so that you can identify these patterns.

People with health anxiety hold dysfunctional core beliefs about health and illness. 
One dysfunctional belief held by those with health anxiety is the overestimation of the probability and severity of disease. Core beliefs are reinforced by information processing, in which we pay more attention to data that confirms our belief.

People with health anxiety hold dysfunctional core beliefs about health and illness. Core beliefs develop early in life and are strengthened through a process of reinforcement. It can be helpful to identify significant life experiences that led one to develop dysfunctional core beliefs about health. Once dysfunctional core beliefs are identified, one can reshape them through cognitive restructuring.