Quantitative evaluation of the effects of disinfectants against viruses in suspension experiments.

Time concentration relations in virus-disinfection by formaldehyde, benzalkonium-chloride, ethanol and isopropanol are evaluated. The exposure time needed to reduce the number of plaque-forming units (PFU) by 10(-3) (99.9%) at a given disinfectant concentration was determined. Influenzavirus, Coxsackie B viruses, Herpesvirus and Mumpsvirus were used in the experiments. Formaldehyde is effective at very low concentrations, provided that sufficient time is allowed for reaction, but has little use in short-term applications. Alcohols act very rapidly at the optimal concentration, but are almost completely ineffective if the reagent is only slightly diluted. Isopropanol does not neutralize entero-viruses to any considerable extent. The effect of the alcohols on viruses is greatly enhanced by the addition of alkali. An 80% (or higher) ethanol solution containing 0.01 n NaOH is very promising as a potent antiviral disinfectant for skin and surface decontamination. Even closely related virus types may differ greatly in their sensitivity to ethanol. The Herpesvirus hominis has a peculiarly high sensitivity to benzalconiumchloride, a sensitivity which is not shared by the Influenzavirus and enteroviruses.