Causes cancers, AIDS Retrovirus ??? ??? ??? Disease-causing agent, such as a bacterium or fungus (479) Pathogen ??? ??? ??? Injection of a weakened or mild form of a pathogen to produce immunity (1040) Vaccine ??? ??? ??? Compound that blocks the growth and reproduction of bacteria (480) Antibiotic ??? ??? ??? Single-stranded RNA molecules that have no surrounding capsids (490)