Thoughts are viruses. Images are viruses. Objects are viruses. Chairs are viruses. Guns are viruses. Adam Lanza's mom bought those guns for home defense, a point that was lost in the blather about the "extraordinary testimony" of the mother in support of home defense yesterday in Congress.
Just as some humans are vectors for chairs, humans can also be vectors for guns.
In future archaeological digs by aliens, some parts of Earth will have enormous strata of chair parts and others will have layer upon layer of gun parts.