Contaminate

verb

1. To make something dangerous or toxic by introducing impurities or foreign matter.

   "This water is contaminated. It isn't safe to drink."

2. To soil, stain, corrupt, or infect by contact or association.
3. To make unfit for use by the introduction of unwholesome or undesirable elements.

   "Do not contaminate the peanut butter with the jelly."

4. To infect, often with bad objects