[thackney]

can only be contracted by sexual contact

...many infectious agents, including viruses, bacteria, and parasites, can be transmitted through blood transfusion. Well-recognized viruses include hepatitis..., and human parvovirus (HPV-B19).

http://www.phac-aspc.gc.ca/hcai-iamss/tti-it/risks-eng.php

[matthew fuller]

Mosquitos are the world’s deadliest critter. Interesting description here- https://secure.wikimedia.org/wikipedia/en/wiki/Mosquito-borne_disease