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DIS/TSS-7 / Nov. 12, 1981

(Proposed method prepared by Registration Division,
Office of PesticidePrograms, EPA, 1976)

The Agency will accept adequate data developed by any virological technique which is recognized as technically sound, and which simulates to the extent possible in the laboratory the conditions under which the product is intended for use. For virucides whose use-directions identify the product as one intended for use upon dry, inanimate, environmental surfaces (such as floors, tables, cleaned and dried medical instruments, etc.), carrier methods, which are modifications of either the AOAC Use-Dilution Method (for liquid surface disinfectants) or the AOAC Germicidal Spray Products Test (for surface spray disinfectants), must be used in the development of the virological data. To simulate in-use conditions, the specific virus to be treated must be inoculated onto hard surfaces, allowed to dry, and then treated with the product according to the directions for use on the product label. One surface for each of two different batches of disinfectant must be tested against a recoverable virus titer of at least 104 from the test surface (petri dish, glass slide, steel cylinder, etc.) for a specified exposure period at room temperature. The virus is then assayed by an appropriate virological technique. The protocol for the viral assay must provide the following information:

  1. The virus recovery from a minimum of 4 determinations per each dilution in the assay system (tissue culture, embryonated egg, animal infection, or whatever assay system is employed).

  2. Cytotoxicity controls: The effect of the germicide on the assay system from a minimum of 4 determinations per each dilution.

  3. The activity of the germicide against the test virus from a minimum of 4 determinations per each dilution in the assay system.

  4. Any special methods which were used to increase the virus titer and to detoxify the residual germicide.

  5. The ID-50 values calculated for each assay.

  6. The test results shall be reported as the reduction of the virus titer by the activity of the germicide (ID-50 of the virus control less the ID-50 of the test system), expressed as log10 and calculated by a statistical method (Reed and Muench, 1938; Litchfield and Wilcoxon, 1949; as examples).

  7. For virucidal data to be acceptable, the product must demonstrate complete inactivation of the virus at all dilutions. When cytotoxicity is evident (as in attached tables) at least a 3-log reduction in titer must be demonstrated beyond the cytotoxic level. The calculated viral titers must be reported with the test results.

A typical laboratory report of a single test with one virus (recovered from a treated surface) involving a tissue culture, therefore, would include the details of the methods employed and the information in the attached tables.

Claims of virucidal activity for a product must be restricted to those viruses which have actually been tested. Separate studies on two batches of product are required for each virus.


Litchfield, J. T., Jr., and F. Wilcoxon. 1949. A simplified method of evaluating dose-effect experiments. Jour. Pharma. Exp. Therapy, 96: 99-113.

Reed, L. J., and H. Muench. 1938. A simple method of estimating 50 per cent end-points. Amer. Jour. Hygiene, 27: 493-497.

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