The State Accident Insurance Fund appeals from a Vorkers’ Compensation Board finding that the claim-mt’s condition is compensable as an occupational disuse. SAIF contends that the claimant is not entitled o the statutory presumption of firemen’s occupational iseases and that he has not shown by a preponderance f the evidence that his disease is work related. We everse.

The claimant worked as a fireman for the City of ilamath Falls from 1967 until September, 1976, when ericardial (heart-related) and pleuritic (lung-related) ains forced him to stop working. He had undergone ledical examinations prior to his employment which ad revealed no cardiac or respiratory problems. Ap-arently the claimant first experienced pleuritic pain lortly after a serious fire at which he had breathed uper-heated smoke. The heart pains, he testified, had egun before the fire.

Early in the course of treatment the treating doctor ispected the pains were caused by a viral infection of re pericardium, the membrane surrounding the eart. The infection was thought to have affected both íe pericardial and pleural membranes, causing heart ad respiratory pain. In a letter to SAIF in late 1976, íe treating doctor dismissed the idea that the condi-on arose out of the claimant’s employment, stating atly that "[t]he disease obviously was not caused by s work.” At the same time, the doctor acknowledged íat work aggravated the pain: "He has had aggrava-on, however, of chest pain on working long hours and as had a fall which seemed to make his chest pain orse. It would seem reasonable to assume that his ain was aggravated by his work activities.”

The continuation of the claimant’s pain has baffled e doctors who have dealt with his case. He was tested ; the Mayo Clinic, the University of Oregon Health :iences Center, and the Portland Pain Center. Open-ftart surgery relieved the pericardial pain for a short *282 while. Tests on pericardial tissue excised during surgery did not aid diagnosis. The results of psychological testing at the Pain Center suggested the possibility that a fear of death and an underlying desire to avoid a return to his dangerous occupation may be the psychosomatic cause of the continuation of the pain. The suggestion, however, was in the nature of speculation, not scientific conclusion. Otherwise, the diagnoses resulting from tests and surgery were that the condition was idiopathic (that is, of no known origin) or organic.

The claimant relies on ORS 656.802 to support his claim for an occupational disease. It provides:

"(1) As used in ORS 656.802 to 656.824, 'occupational disease’ means:

"* * * * *

"(b) Death, disability or impairment of health of firemen of any political division who have completed five or more years of employment as firemen, caused by any disease of the lungs or respiratory tract, hypertension or cardiovascular-renal disease, and resulting from their employment as firemen.

"(2) Any condition or impairment of health arising under paragraph (b) of subsection (1) of this section shall be presumed to result from a fireman’s employment. However, any such fireman must have taken a physical examination upon becoming a fireman, or subsequently thereto, which failed to reveal any evidence of such condition of impairment of health which preexisted his employment. Denial of a claim for any condition or impairment of health arising under paragraph (b) of subsection (1) of this section must be on the basis of medical or other evidence that the cause of the condition or impairment is unrelated to the fireman’s employment.”

ORS 656.802 was amended in 1977. 1

*283 In Wick v. SAIF, 37 Or App 285, 587 P2d 477 (1978), we considered without deciding whether the statute as unended or in its preamendment form ápplies to a condition which arose before the 1977 amendment but which is being reviewed after the amendment. We ;onclude that the 1977 amendment is merely a reword-ng of the preexisting statute, intended to clarify rather than to modify it. Although the legislature hanged the phrase "disputable presumption” to ¡imply "presumption,” the last sentence of the amend-sd statute shows that the presumption is still a disputable one. Therefore, under either version of the stat-ite, our analysis is the same.

As we recognized in Pflughaupt v. SAIF, 26 Or App 77, 80, 552 P2d 284 rev den (1976), a disputable pre-umption stands when it is not opposed by evidence, iut falls with the introduction of opposing evidence.

"* * * [T]he Oregon legislature intended that the presumption apply and bind the jury only where there is no opposing evidence. If there is some opposing evidence, the trier of fact may consider all evidence on both sides and come to its own conclusion. If the evidence is in equipoise, the trier of fact must find for the defendant because the plaintiff had not met his burden of proof.” (Footnote omitted.)

In Wick v. SAIF, 37 Or App at 288, we applied the isputable presumption rule to firemen’s occupational iseases:

"* * * [T]he fireman’s presumption disappeared the moment that any significant evidence that a *284 claimant’s condition was not caused by employment as a firefighter was introduced. The decision was then to be made strictly by weighing the evidence and determining whether the claimant had proven causation by a preponderance.” (Citations omitted.)

In this case, there is significant evidence to dispute the presumption that this is an occupational disease. The statement of the treating physician that "[t]he disease obviously was not caused by his work” is sufficient evidence to eliminate the presumption.

We therefore weigh the evidence. In claimant’s favor is the fact that the first medical evidence of any heart or respiratory condition was found shortly after the claimant had fought a serious fire. In addition there is the suggestion, but no conclusion, that a fear of the dangers of his job may cause the pains.

However, we do not find that this evidence outweighs the evidence contained in the mass of medical reports that have accumulated regarding the claimant. We acknowledge that the physicians cannot affirmatively state the cause of the disease, but we also note that they consider the cause to be organic, or in other words, to be not work related.

Having determined that this condition was not caused by the claimant’s occupation, we next consider whether the claimant’s occupation had caused a com-pensable aggravation of his condition. The evidence tends to show that firefighting work stimulated the claimant’s pain, but there is no evidence that the firefighting aggravated the underlying condition. This is not sufficient to establish a claim. In Weller v. Union Carbide, 288 Or 27, 35, 602 P2d 259 (1979), the Supreme Court held that to prevail, the worker must prove that the work activity or condition caused the underlying disease or a worsening of it. See also Henry v. SAIF, 39 Or App 795, 593 P2d 1251 (1979). We cannot find that the claimant’s employment affected anything more than the symptoms of his disease.

*285 In conclusion, claimant has not proved by presump-ion or by a preponderance of the evidence that his íeart condition was either caused or aggravated by his smployment. We reverse the Workers’ Compensation loard and deny the claim for compensation.

Reversed.