Actually, most of the ticks that transmit Lyme Borrelia to us are nymphs, which seek out small mammals on which to feed. This stage of the tick is most active in the summer months, when people are spending lots of time outside, whereas the adult stage, which feeds and mates on deer, is most active in the late fall. It is a fascinating and complex biology, and like most biological systems, we pretty much just get in the way.