**3. Overview of chemical viral inactivation approaches**

Viral inactivation may be achieved by chemical and/or physical methods. The subset of chemicals commonly used for inactivation of non-enveloped viruses includes alcohols, oxidizers, halogen compounds, quaternary ammonium compounds, phenolics, aldehydes, acids, and alkalines [17–19]. These differ with respect to efficacy, stability, toxicity, material or surface compatibility, cost, and sensitivity to organic soil load. Soil load is a term used to signify an organic matrix used to challenge the inactivating efficacy of a microbicide. It is intended to mimic secretions or excretions in which the virus would be released from an infected person or animal. Some chemistries (e.g., sodium hypochlorite, phenolics, and aldehydes) are mostly used for environmental or medical device disinfection. Other chemistries (e.g., ethanol) are more commonly used for hand hygiene, while some others (e.g., quaternary ammonium compounds) may be used for both environmental disinfection and skin antisepsis (**Table 2**).

The virucidal efficacy of a product is not only determined by the type and concentration of the chemical, but is also heavily influenced by the formulation, pH, exposure (contact or dwell) time, organic soil load, temperature, and surface characteristics (as applicable), etc. [10, 20–22]. Given the differences between various testing methods, as well as the intrinsic variability of viral infectivity (titration) assays, a general conclusion on the efficacy of a particular type of active ingredient will be enhanced if the efficacy is derived from multiple sets of data and under various application conditions (such as the concentration of the microbicidal active(s), contact time, formulation matrix (as applicable), and organic soil load, etc.) Additionally, in order best to explore the relative ranking of susceptibility between viruses, or the lack thereof, efficacy data from side-by-side studies wherein the same test methodologies and conditions were used would be preferable. Care should be taken when comparing data from different studies, especially if the formulations, test methods, and test conditions were different.
