Internet Savvy Lacking in Europe? A Question of Viruses

I was just using the TrendMicro free HouseCall anti-virus scan and noted at this page that in the last 30 days TrendMicro had found 5 times as many infected files in Europe as in the USA.

What can the reason for this be? Is Internet savvy lacking in Europe? or are there just more viruses around in the Old World? or are more European users using this free service? and would that be a sign of the more dire EU economic situation?
.