Some infections come in repeated epidemic waves, others are new to human populations. A known human threat such as influenza may mutate or a new infection jumps the species barrier from animals to humans: recent examples include HIV and Ebola, and the historical example of plague. What happens depends on the route of transmission.
Methods for tackling an airborne disease like influenza are different from those for touch (Ebola), insect vector (Zika), water (cholera) or sexual transmission (HIV).
Gresham College has been giving free public lectures since 1597. This tradition continues today with all of our five or so public lectures a week being made available for free download from our website. There are currently over 2,000 lectures free to access or download from the website.