Typically any type of virus is dependent on several things but here are the few that I think about when I am investigating an outbreak: 1) The virus or bacteria involved 2) Incubation period of said virus/bacteria once a person is exposed 3) A susceptible host 4) Route of transmission 5) Know vehicles of transmission (example as you all have identified hand-shaking, coughing, to name a few). 6) General public awareness and whether they are using precautionary recommendations identified in PSA message.
With a Pandemic virus, the challenges are exponential and government health agencies around the world have tackled the theoretical to the inth...as I've mentioned in a previous thread the challenge will be for even say local or national health departments, how to control the whats? when? and where?. The likelihood of an airborne virus infecting the entire world is not a remote possibility, but a real possibility because of air travel today. The farther you are from a port of entry, I've named a few in previous ones, but all you have to do is google all the international port of entries for your country...and then "X" them on a map, you can then run concentric rings based on the etiology of the virus to gather a good hypothesis and time index of what precautions and level of response you need to carry out in that type of scenario. For example, when would you got to a level of just using surgical mask/faceshield to a true gas mask with filter. When would you establish your pandemic controls.
For the common cold, all of us have been taught to increase hand-washing, but how many actually do it. As Brent S indicated earlier, he works in the public, its going to be difficult to go to work with a mask on...for me, I'd advise your boss that your sick...and you don't want anyone else to get sick. Quick explanation that doesn't have to be validated and the same time you've establish some protocols from your Pandemic response checklist.