(1) The terms “injury” and “personal injury,” as used in this act, shall be construed to mean an injury to an employe, regardless of his previous physical condition, except as provided under subsection (f),¹ arising in the course of his employment and related thereto, and such disease or infection as naturally results from the injury or is aggravated, reactivated or accelerated by the injury; and wherever death is mentioned as a cause for compensation under this act, it shall mean only death resulting from such injury and its resultant effects, and occurring within three hundred weeks after the injury. The term “injury arising in the course of his employment,” as used in this article, shall not include an injury caused by an act of a third person intended to injure the employe because of reasons personal to him, and not directed against him as an employe or because of his employment; nor shall it include injuries sustained while the employe is operating a motor vehicle provided by the employer if the employe is not otherwise in the course of employment at the time of injury; but shall include all other injuries sustained while the employe is actually engaged in the furtherance of the business or affairs of the employer, whether upon the employer's premises or elsewhere, and shall include all injuries caused by the condition of the premises or by the operation of the employer's business or affairs thereon, sustained by the employe, who, though not so engaged, is injured upon the premises occupied by or under the control of the employer, or upon which the employer's business or affairs are being carried on, the employe's presence thereon being required by the nature of his employment.

(2) The terms “injury,” “personal injury,” and “injury arising in the course of his employment,” as used in this act, shall include, unless the context clearly requires otherwise, occupational disease as defined in section 108 of this act:² Provided, That whenever occupational disease is the basis for compensation, for disability or death under this act, it shall apply only to disability or death resulting from such disease and occurring within three hundred weeks after the last date of employment in an occupation or industry to which he was exposed to hazards of such disease: And provided further, That if the employe's compensable disability has occurred within such period, his subsequent death as a result of the disease shall likewise be compensable. The provisions of this paragraph (2) shall apply only with respect to the disability or death of an employe which results in whole or in part from the employe's exposure to the hazard of occupational disease after June 30, 1973 in employment covered by The Pennsylvania Workmen's Compensation Act. The employer liable for compensation provided by section 305.1³ or section 108, subsections (k), (l), (m), (o), (p), (q) or (r), shall be the employer in whose employment the employe was last exposed for a period of not less than one year to the hazard of the occupational disease claimed. In the event the employe did not work in an exposure at least one year for any employer during the three hundred week period prior to disability or death, the employer liable for the compensation shall be that employer giving the longest period of employment in which the employe was exposed to the hazards of the disease claimed.