That’s a good theory. You’re right that cancer ‘lumps’ probably look similar to the Black Death lumps, and these were caused by bites from fleas – which infected people with a bacterium called Yersinia pestis.
But we know that this is not the case for cancer: cancer is caused by your own cells mutating, and fleas/parasites have nothing to do with this.
While I’m sure some parasites or fleas could increase the risk of cancer, either by releasing cancer-causing toxins or by habouring cancer-causing viruses, I don’t think that the black death was cancer-related, because the lumps appeared too quickly.
That’s a great theory – and it shows that you are getting the hang of thinking like a scientist! You have observed some natural phenomena and are trying to find connections and patterns to link them together – I’m sure you’d make a fine scientist!
However, the two are not related – the swellings from bubonic plague are swollen lymph nodes caused by the infection. In cancer, however, the lumps (tumours) are collections of cells which have divided rapidly out of control – and can occur almost anywhere in the body.
Good thinking, though – what other things do you see happening in the world which could be related, and could you come up with an experiment to try and test out that theory?
I’ve never heard of any parasites that cause cancer, but I don’t know everything about cancer.
The lumps that you get in cancer are balls of cells that have grown out of control, whereas the lumps in The Black Death were swellings from the body reacting to an infection, so they were quite different. The Black Death wasn’t caused by the fleas themselves, but by a bacteria that got into people when they were bitten by fleas.
There are some bacteria that can increase the risk of getting cancer. The one I know about is called Helicobacter Pylori – and it increases the risk of stomach cancer.
Some viruses are called transforming viruses for their capacity to transform the cell into a cell that divides indefinitely (that is a cancer cell). This is the case for papilloma virus (HPV) whose infection increases the risk of cervical cancer and Epstein-Barr virus, that can lead to Burkitt’s Lymphoma. Years ago, when they hadn’t discovered yet the genetic origin of cancer, scientists thought that all cancers were provoked by a virus.