What Causes Cancer?
More than 100 years ago, researchers thought cancerous tumors might be caused by viruses and other infectious agents. In the decades that followed, their attempts to verify this theory failed. Introduction of various infections into animals usually did not yield cancer, according to the Scientific American. Gradually, the theory fell out of favor.
Over the past 20 years, investigators have linked several types of cancer to viruses, bacteria or parasites. According to the Scientific American, about five percent of cancer fatalities in the U.S. result from diseases brought on by infections.
What causes the other 95 percent? Researchers have yet to crack the code on the reasons cell growth spins out of control. But chemicals, radiation, viruses, hormones and inherited mutations can act together to start or further cancer. In fact, researchers say that the top two causes -- tobacco and diet -- account for almost two thirds of all cancer deaths and are among the most correctable.
More Information:
- Scientific American: Cancer's Causes
- National Cancer Institute: Risk Factors And Possible Causes
Image from the National Cancer Institute.
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