Can math help understand disease?

A big question I know but a useful one. Some people are [using math to kill cancer cells][1]. Can you think of any ways you could use maths to understand disease better? It's a broad question so I'm happy with broad answers. It's more of a brainstorm and topic starter than a question with a specific end point. Here's an example that might help. John Snow in 1854 figured out that cholera was carried in contaminated water using basic maths. Back then everyone got their water from public wells. He had a hunch that a particular well was the source of the outbreak in London. He just asked everyone who caught cholera where they got their water. Only people who got their water from the well got cholera. Doesn't sound difficult now but it was ground breaking then. These days we use much more complicated forms of maths to essentially do the same thing. Prove that the results show what we think they show. That's maths helping us do research and understand disease. Have you got any examples? [1]: http://www.biocompare.com/Life-Science-News/139591-Using-Math-To-Kill-Cancer-Cells/