But, another species provides a glimpse at just how bad a contagious cancer could be if one arose. Twenty years ago, a single Tasmanian Devil experienced had a mutation that created a directly contagious cancer (no intervening virus is required). It is passed from one individual to another through bites. The cancer attacks the same part of the body as M.S. (sheathing around nerves). In the past twenty years:
About 70 percent of the Tasmanian devil population has disappeared as a result of the disease, and if the current rate of decline continues, devils could become extinct in the wild in 30 to 50 years[.]
This cancer is hitting the species more heavily than the black plague did humans in the middle ages, and almost as badly at smallpox did populations in the New World making first contact. At this point there is no cure.
One hopeful possibility is that this cancer can only be contagious because Tasmanian Devils are so deeply inbred.
Tasmanian devils are so genetically similar to one another that their immune systems don’t recognize infectious cancer cells from another individual as foreign[.]
Still, if you are short on bogeymen, contagious cancer will make a nice addition to your list of truly terrifying threats to humanity.