Additionally, unlike bacteria, which to date still have many antibiotics that are effective against them, the very nature of the biology of viruses has made antiviral agents difficult to produce. The common cold is spread by airborne droplets from an infected person breathing, coughing, or sneezing. Viruses will generally not stay alive on inanimate objects long enough to be a problem, as on a phone for instance. The droplets must be inhaled. However, when considering any infection, one must keep in mind a number of things.
Infection is by no means automatic.
Just because a person is exposed to an infection does not mean that an infection will ensue. Virulence refers to the inherent ability of a particular organism to cause infection. Some strains may have a low infectivity rate while others have a higher one. Host resistance refers to the immunological state of the person exposed. What this means is that if two people are standing side by side when an infected person sneezes directly into their faces and we assume that they both receive the same number of organisms into their airways, it is possible that one or both of them may not get sick.