I'm thinking that the best way to avoid having any germs transmitted from client-to-client or to the reader would be to not have clients handle the deck for the time being.
If there's any sort of bug going around, H1N1 or otherwise, avoiding having multiple people handle the deck one after another will help remove one possible route of transmission.
Once upon a time, I was one of the interpreters at a meeting of a regional organization for deaf-blind people. Most of the deaf-blind at the meeting communicated via tactile sign language (where one person signs directly into the other person's hands). On the day of the meeting, one person in attendance had a headcold.
Then everybody talked to everybody else, including a ton of hand-to-hand contact between deaf-blind members or between members and interpreters. In a week, EVERYBODY I knew who was at the meeting, including myself, had a headcold.
This was a few years before hand sanitizers existed, unfortunately. The first time I saw Purell, I thought of that deaf-blind group meeting and I wanted to give the inventor of hand sanitizers a Nobel Prize. Even though they're not antiviral, stopping SOME kinds of germs from spreading is better than nothing.
In any event, to drag this post back on topic, my experience at the Headcold Meeting
leaves me thinking that having multiple people handle a deck during a time when there's some sort of bug going around is tempting fate.