**2. Common families of mammalian non-enveloped viruses**

Currently, there are a total of 21 families of viruses (including enveloped and non-enveloped) identified for humans [13], which represent only a small part of the entire paradigm of viruses in nature, whose host ranges extend from vertebrates to plants to bacteria. The most common families of non-enveloped viruses for humans and animals include *Adenoviridae, Astroviridae, Caliciviridae, Circoviridae, Hepeviridae, Papillomaviridae, Parvoviridae, Picornaviridae, Polyomaviridae,* and *Reoviridae.* The genome structure, size of viral particle, and some representative viruses for each viral family are presented in **Table 1**.

Among these, the *Adenoviridae and Reoviridae* families of viruses are generally considered large, non-enveloped viruses. Other non-enveloped viruses are generally considered small, non-enveloped viruses, although it should be noted that the particle sizes of *Papillomaviruses* and *Polyomaviruses* are notably larger than those for the rest of the small non-enveloped virus group (**Table 1**).

It is worth noting that viruses are typically classified taxonomically on the basis of virion properties (size, shape, envelope, physical, and chemical properties, etc.), genome organization, replication mechanism, antigenic properties, and biological properties [13–15]. The final classification is a combined consideration of these properties. However, the stability and susceptibility to inactivation of a virus may not relate to all of these properties and, as such, may not always align with the taxonomic classification system. For example, the susceptibility of a virus to surfactants may primarily be related to the envelope of the virion and not related to the genome structure or mode of replication.

The susceptibilities of non-enveloped viruses to chemicals have been found to be highly variable and somewhat hard to predict, since they do not always agree with the hierarchy concept. For example, according to the hierarchy concept as modified by Sattar [8], small non-enveloped viruses should be less susceptible than large nonenveloped viruses. Additionally, if there is a fixed hierarchy, all small nonenveloped viruses should either display similar levels of susceptibility or should demonstrate a definitive trend of relative susceptibility, regardless of the type of microbicide. Based on the literature, neither of these predictions appear to hold in every case. The relative order of susceptibility seems chemistry-dependent; and sometimes viruses within the same family or even genus have been found to exhibit unequivocal differences in their susceptibilities (reviewed in [16]). Any trending or


#### **Table 1.**

*Common families of human and animal non-enveloped viruses.*

hierarchy, therefore, must be reviewed in the context of the type of chemistry, and it should not be assumed that non-enveloped viruses within the same family or genus will always display similar susceptibilities to a given microbicide.

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