virus (6) air (6) Air (6) resistance (6) DNA (5) aerosol (5) Viruses (5) DNA (5) Viruses (5) DNA (5) sampling (4) assay (4) (4) Environmental conditions (4) Sampling (4) Plasmids (4) Bacteriophages (4) Sampling (4) time (3) stable (3) family (3) exposure (3) detection (3) method (3) Variation (3) Double-stranded RNA (3) Time (3) Streptococcus thermophilus (3) Streptococcus salivarius (3) Streptococcus (3)