virulence genotypes
virulence markers
virulence mechanisms
virulence phenotype
virulence plasmid
virulence potential

virulence properties
virulence protein
virulence regulator
virulence traits
virulent
virulent form
virulent parasites

virulent pathogens
virulent strains
virus
virus 35S promoter
virus accumulation
virus activity
virus antibodies

virus antigens
virus assembly
virus binding
virus C
virus DNA
virus DNA levels
virus RNA

virus X protein
virus Y