Factors influencing quantitative isolation of varicella-zoster virus

Optimal conditions are described for the recovery of cell culture-derived varicella-zoster virus (VZV). Of the cells tested, human embryonic lung fibroblasts were the most sensitive. Storage and handling procedures were examined to determine the stability of VZV in viral transport medium. When the initial VZV titer was high (2 X 10(4) PFU/ml) 40% of the VZV survived room temperature for 24 h and 75% of the VZV remained viable for this long at 4 degrees C. Recovery was 5- to 10-fold less at lower initial VZV titers (less than 2 X 10(3) PFU/ml). Other factors which influenced VZV recovery included freezing at -20 degrees C, the use of cotton or calcium alginate swabs, and filtration to remove bacterial contaminants. The tissue culture methods described were used in a reconstruction experiment to demonstrate that VZV could be recovered from a laboratory coat or human skin (0.1 to 0.3% of input VZV) or from a stethoscope (19% of input VZV) as late as 30 min after inoculation. During a clinical trial using optimal VZV recovery procedures, 76% of the patients with herpes zoster yielded VZV when first cultured, and 60% remained culture positive for an additional 48 h.