Hugo Chávez, the late leader of Venezuela, passed away this month after a long battle with cancer. A charismatic public personality, he managed to turn even this very private battle with a debilitating disease into an attack on the United States, as he openly speculated if the U.S. could have infected him with cancer. That raises some interesting questions – can cancer be transmitted? Is it even possible for the U.S. government to intentionally infect another person with cancer?
When scientists first started studying cancer in earnest in the early 1900s, they focused primarily on viral cancers that infect birds and could be transmitted from one bird to another via the blood. Even today, there is some evidence for viral cancers – a single facial cancer is currently decimating the population of Tasmanian devils, because it is transmitted when they bite each other while fighting. Despite the examples in nature, there isn’t much evidence for cancer viruses in humans. The only well-characterized example is human papillomavirus (HPV), which is the main cause of cervical cancer. Since Chávez’s doctors probably knew how to test for HPV, we can reasonably rule that out as a cause. But what about spreading actual cancer cells from one person to another?
The thing about cancer is that it manages to wreak a lot of havoc in our bodies because it avoids detection by our immune system since it looks pretty similar to our normal cells. Cells have lots of “flags” sticking out of their membranes, and your immune system recognizes your body’s “flags;” anything it encounters that doesn’t have the right flags flying gets attacked. Unfortunately, since cancer typically starts out as a normal cell, it does have the right flags displayed, so the immune system leaves it alone. This means that cancer would have a lot of trouble infecting someone else – that person’s immune system would almost always recognize it as an invader and kill it off.
The only other way the U.S. government (or anyone else for that matter) could have infected Chávez with cancer would be by deliberately exposing him to known carcinogens such as UV radiation or cigarette smoke. This is still pretty far-fetched. Yes, carcinogens are known to increase your risk of cancer, but that’s all they do: increase the risk. Very few things are a guaranteed “if you’re exposed, then you’ll get cancer” scenario (other than smoking: that link is pretty solid). Even if it were possible to expose the leader of a foreign government to carcinogens without getting caught, you still wouldn’t even be guaranteed success.