boon23, the symbol is the 'biohazard' symbol. Dictionary.com had this to say about 'biohazard' (I couldn't think of a goodway to describe the meaning):
1. A biological agent, such as an infectious microorganism, or a condition that constitutes a threat to humans, especially in biological research or experimentation.
2. The potential danger, risk, or harm from exposure to such an agent or condition.
2. The potential danger, risk, or harm from exposure to such an agent or condition.
If you want me to drop it from the cover, let me know. I think it's fitting though (and it is plastered all over "28 days later" stuff).