Antiviral activity of an alcoholic hand disinfectant. Comparison of the in vitro suspension test with in vivo experiments on hands, and on individual fingertips.

The inactivation of eleven viruses by a commercial alcoholic hand disinfectant ("Desderman') was tested by three different procedures, viz., in vitro in a standardized suspension test, in vivo on the entire surface of both hands, and in vivo on individual fingertips of a single volunteer. The test protocols were chosen such as to make results comparable. The influence of varying disinfectant/virus volume ratios, serum protein loads, and reaction temperatures was evaluated in vitro, and partly demonstrated in vivo. In some experiments, 5% formaldehyde was included as a reference disinfectant. The experiments support the prevailing concept, that enveloped viruses are considerably more susceptible to alcoholic disinfection than naked ones. Additionally, enveloped viruses were shown to be subject to more "spontaneous' decay on skin. The main result of the study appears to be that the in vitro model predicted a greater effectiveness of the disinfectant than was observed in vivo both in the "hand' test and the "finger' test, although some differences were noted between these tests. Reasons for the lesser in vivo inactivation may lie in the evaporation of the disinfectant with ensuing changes in disinfectant/virus volume ratio, effective temperature, and inactivation time, all shown to influence disinfection. Other mechanisms such as a "sheltering' effect of the skin may have also been operating. The results suggest that, at the present stand of knowledge, in vitro screening tests should be complemented by in vivo tests for the evaluation of antiviral hand disinfectants.