how does the spread of germs vary?

It depends on what the person has. The flu virus is mostly airborne, and spread through coughing and sneezing, but it can also be spread when a sick person who has coughed or sneezed into his hand touches you. The amount of germs you would receive is unknown...it would depend on how much mucus the person had on his hand. When a person with the flu coughs or sneezes, it sends little droplets of moisture into the air, and they can land on anything and live there for several days. So how many germs are on the surface that you could pick up would also depend on how long they have been there. The fresher the droplets or mucus, the more germs there will be. You should be careful of door knobs, handles, toilet handles sink faucet handles, counter tops,..things like that. If the sick person has been on antibiotics for a few days, they may no longer be contagious, depending on what they have. However, you cannot kill a virus, so this does not pertain to the cold or flu. Your best bet to prevent getting sick, is to wash your hands often, and try not to touch your face (eyes, nose) before they are washed. Germs can enter your body through the mucus membranes in the nose and eyes when you have germs on your hand and then touch your face. If you can't get to a sink to wash with soap and hot water, use an antibacterial waterless hand gel, or antibacterial hand wipes. These are good to have with you when you are at a mall or store. I keep them in my car and purse......

well most cases you get sick from not washing your hands after being in contact with germs. Sneezing and coughing is also a likely result, through air borne germs. Don't kiss them as well :P

It depends if you touched them or not, but anyway there is airborne germs that you will be in contact with even if you didnt touch them, no accurate way of knowing "the amount of germs"

It depends if they are coughing, gagging, sneezing, not washing their hands and touching you. There's no "amount" of germs you'll get. It depends on how cautious you are to prevent getting sick.

They spread by direct contact (ie contaminated foods,sexual contact), indirect contact (patient to patient on the hands of a health care worker, MRSA), droplet contact (inhaling droplets that cannot travel > 3 ft, pertussis), airborne contact (inhaling droplets that can travel long distances on air currents, TB), and vector-borne (malaria, rat-bite fever).