**4. Inactivation of non-enveloped viruses by alcohols**

Alcohols, primarily ethanol and isopropanol, are widely used for hand hygiene and environmental disinfection, and their efficacies against bacteria and viruses have been extensively studied [23–25]. Ethanol at a concentration of 70–90% and isopropanol at 70% have been broadly shown to be effective against enveloped viruses; however, their efficacies against non-enveloped viruses are much more variable.

The trending of the degree of susceptibility of non-enveloped viruses to ethanol and isopropanol is generally clearer and more consistent than it is for many other types of chemistries, thanks to the large amount of data in the literature. The relative ranking of susceptibility of non-enveloped viruses seems to differ between ethanol and isopropanol; and the ranking does not appear to align well with the classical virological taxonomy.

For ethanol, parvoviruses and the polyomavirus simian virus 40 have low susceptibility, while rotavirus (a reovirus) is susceptible (**Table 3**). Viruses in the *Picornaviridae* family display clear differences in their susceptibilities to ethanol; and even viruses within the same genus display marked differences. For example, hepatitis A virus and human enterovirus 71 are much less susceptible than rhinovirus; and poliovirus, foot-and-mouth disease virus, and coxsackie virus seem to exhibit intermediate levels of susceptibility compared with the aforementioned viruses. The viral family *Caliciviridae* also has shown drastic differences among family members in the susceptibility to ethanol. Murine norovirus is quite susceptible to ethanol, whereas


*Abbreviations used: BKC, benzalkonium chloride; Conc, concentration; DDAC, didecyldimethylammonium chloride; HLD, high-level disinfection; NaOH, sodium hydroxide; OPA, ortho-phthaldehyde; QAC, quaternary ammonium compounds.*

#### **Table 2.**

*Common types of chemistries used for non-enveloped viral inactivation.*

feline calicivirus, human norovirus, and Tulane virus are significantly more difficult to inactivate with ethanol. The *Adenoviridae* is another non-enveloped virus family that has shown intrafamily differences, wherein adenovirus 5 is rather susceptible but adenovirus 2 and adenovirus 8 are much less susceptible. The relative order of susceptibility between murine norovirus (a small, non-enveloped virus) and adenovirus types 2 and 8 (two large, non-enveloped viruses) clearly conflicts with the simplified hierarchy concept (**Figure 1**).

Interestingly, the above order of susceptibility does not appear to hold the same for isopropanol (**Table 3**). For example, the polyomavirus simian virus 40 is much more susceptible to isopropanol than many other non-enveloped viruses; and poliovirus appears to display a lower susceptibility, similar to that of hepatitis A virus and human enterovirus 71. Murine norovirus is still more susceptible than


*Variability and Relative Order of Susceptibility of Non-Enveloped Viruses to Chemical… DOI: http://dx.doi.org/10.5772/intechopen.102727*


*a See Table 1 for abbreviations used for viruses. <sup>b</sup>*

*BSA, bovine serum albumin; medium, culture medium; RT, room temperature.*

*Entries in purple font indicate results from undiluted or diluted formulations with the indicated microbicidal active ingredients.*

#### **Table 3.**

*Efficacy of alcohols against non-enveloped viruses.*

feline calicivirus to isopropanol, but not as susceptible as simian virus 40 or rotavirus. The apparent difference between adenovirus 5 and adenovirus 8 that has been observed for ethanol has not been observed for isopropanol.
