Indiana Code Title 22. Labor and Safety § 22-3-7-10

Sec. 10. (a) As used in this chapter, “occupational disease” means a disease arising out of and in the course of the employment.  Ordinary diseases of life to which the general public is exposed outside of the employment shall not be compensable, except where such diseases follow as an incident of an occupational disease as defined in this section.

(b) A disease arises out of the employment only if there is apparent to the rational mind, upon consideration of all of the circumstances, a direct causal connection between the conditions under which the work is performed and the occupational disease, and which can be seen to have followed as a natural incident of the work as a result of the exposure occasioned by the nature of the employment, and which can be fairly traced to the employment as the proximate cause, and which does not come from a hazard to which workers would have been equally exposed outside of the employment.  The disease must be incidental to the character of the business and not independent of the relation of employer and employee.  The disease need not have been foreseen or expected but after its contraction it must appear to have had its origin in a risk connected with the employment and to have flowed from that source as a rational consequence.