Dr. Greene's Answer
When someone has a cold, the nasal secretions are teeming with cold viruses. Coughing, drooling, and talking are all unlikely ways to pass a cold. But sneezing, nose-blowing, and nose-wiping are the means by which the virus spreads. You can catch a cold by inhaling the virus if you are sitting close to a sneeze, or by touching your nose, eyes, or mouth after you have touched something contaminated by infected nasal secretions.
Once you have “caught” a cold, the symptoms begin in 1 to 5 days. Usually irritation in the nose or a scratchy feeling in the throat is the first sign, followed within hours by sneezing and a watery nasal discharge.
Inhaling droplets from coughs or sneezes is the most common way to catch the flu. Symptoms appear 1 to 7 days later (usually 2-3 days). The flu is airborne and quite contagious, and with its short incubation period it often slams into a community all at once, creating a noticeable cluster of school and work absences. The flu usually arrives in the winter months. Within 2 or 3 weeks of its arrival, most of the classroom has had it.