It happens to me, travelling regularly to the US. I so often end up with a cold that comes on a day or two after I arrive. I'm not convinced it's the surfaces that I come into contact with - after all I'm forever coming into contact with "shared" surfaces. I do believe it's principally the disruption to normal sleep patterns that reduces the body's ability to fight infection that is the culprit. Add that to close proximity to people who themselves have infectious colds and it's a heady cocktail.
Using First Defence (that's the UK name - I've never found it in the US) as soon as I start feeling the slightest bit odd has helped hugely but I still am "off-color" on about 1/3 of my winter trips.