The Virucidal Effectiveness of Towelettes Test verifies the capability of single-use, pre-impregnated towelettes (otherwise known as germicidal wipes) to inactivate viruses inoculated onto hard, nonporous surfaces. The test is intended to replicate consumer use of the towelettes and is conducted according to the standards and methods accepted by the U.S. Environmental Protection Agency (EPA) for registration of the product as a virucide.
Virucidal Efficacy Guidelines

The U.S. EPA recommends the use of internationally-recognized standard test methods as the basis for pre-saturated towelette virucidal efficacy evaluations:

  • AOAC Germicidal Spray Products as Disinfectants Test, Modified for Wipes
Brief Summary of the Test

The U.S. EPA recommends the use of internationally-recognized standard test methods as the basis for pre-saturated towelette virucidal efficacy evaluations:

  • Two lots/batches of pre-saturated towelettes are evaluated for testing. Approved surrogate viruses are tested in duplicate, all other viruses are tested in singlet.
  • If requested by the Study Sponsor, the test virus is loaded with organic soil to the appropriate level.
  • The viral inoculum is spread over the carrier surface(s) and allowed to dry.
  • The dried virus films are wiped with the pre-saturated towelette and held for the specified contact time.
  • At the close of the contact time, the test carrier films are neutralized using a method most suitable for the active ingredient(s) present in the test substance.
  • The test suspensions are assayed for the presence of infectious virus using established methods.
  • Viral plate recovery controls, cytotoxicity and neutralization controls, stock titer determinations, and blank towelette and sterility controls are also performed and assayed in parallel with neutralized test suspensions.
Carrier Options

One of the two following carrier options may be employed per test lot/batch for single-use towelettes testing:

  1. Ten carriers
  • Dried virus inoculum area per carrier: 1” x 1”
  • Ten carriers treated per lot/batch of test towelettes
  • One towelette used to treat ten carriers

  1. Two carriers
  • Dried virus inoculum area per carrier: 10-in.2 equivalent
  • One carrier treated per lot/batch of test towelettes. (Two carriers treated per lot/batch for surrogate viruses)
  • One towelette used to treat each carrier
Virucidal Efficacy Success Criteria

The U.S. EPA requires that the following criteria (among others) be met in order for the test substance to be considered for a disinfectant label claim:

  • Complete inactivation of the test virus at all dilutions of the assay.
  • A 3-log10 reduction of the test virus past the observed level of cytotoxicity. 
Strengths of US EPA Single-Use Towelettes Virucidal Efficacy Testing
  • The method provides flexibility in the selection of test methods and testing parameter modifications (example: number of carriers per lot/batch).
  • At a fundamental level, the method is representative of actual consumer use because the virucidal fluid is applied to the virus-contaminated surfaces by towelette. This means that mechanical factors, such as scrubbing/wiping, are accounted for in the results.

Weaknesses of US EPA Single-Use Towelettes Virucidal Efficacy Testing
  • Differences in carrier treatment parameters (examples: pressure applied to and the number of strokes per carrier) may increase variability in efficacy among study directors and from lab-to-lab.
  • Since the surface area tested with a single wipe is only ten square inches, the volume of virucidal towelette fluid delivered to the test surface is probably greater than that realized during typical consumer use.


Single-Use Towelette Virucidal Efficacy Testing according to U.S. EPA criteria can be performed at Microchem Laboratory as a simple screen (non-GLP), and under more comprehensive GLP study conditions.

Microchem Laboratory Is:

An EPA and FDA GLP-compliant testing organization staffed by skilled, experienced microbiologists and chemists.  Microchem can help speed your project to completion.

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