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SOLID PROOF: CANCER SPREADS

Cancer Virus?

In 1960 a virus was proven to cause a cancer in chickens. It was the first time a virus was found definitely to cause a cancer and the first time a cancer was shown to be contagious. The proof of this finding was affirmed by using Robert Koch's postulates, a set of sensible procedures which eliminate the possibility that there is more than one cause for an effect. First the agent must be isolated from affected individuals and then grown in pure cultures. Next normal individuals exposed to the cultured agent must contract the disease the agent is assumed to cause. Finally the same agent must be isolated from the exposed individuals who contracted the illness.

Researching Sarcoma Cause

Dr. B. R. Burmester of the U.S. Department of Agriculture Regional Poultry Laboratory in East Lansing, Michigan, applied Koch's postulates to the Rous sarcoma virus, assumed to cause a certain type of cancer called sarcoma. Burmester isolated the virus in chickens with sarcoma, cultured it, and injected healthy chickens. Of the forty-five he injected, thirty-five chickens developed sarcomas. From these Burmester isolated the same virus. By Koch's postulates, then, Burmester determined that the virus caused the sarcoma.

The Cancer Connected with Contagious Virus

He continued his experiments. Healthy chickens were placed in cages with chickens injected with the virus. Even those not injected directly developed sarcomas. He concluded that the virus must be contagious. Those who were directly injected developed sarcomas much sooner than their healthy contacts. Also, healthy chickens were placed in cages with injected ones but separated by a wire screen; of these, no healthy chickens developed sarcomas. Direct contact was required for infection.