This is what I have so far but I need to add more any ideas would be great. Thanks. (How does overpopulation cause epidemics)
THe more people that one comes in contact with each day, the more chances there are to pass on or receive a contagious disease. Since society is united in one tightly packed area a widespread outbreak would infect numerous people at the same time.
That's good so far. :-)
Also -- overpopulated areas tend to be poor and many people are malnourished, thus rendering them more susceptible to disease. Overpopulated and poor areas tend to have fewer doctors and other health care workers. Often sanitation is nonexistent or minimal.