*2.5. Possible Clusters of Transmission of SARS-CoV-2*

Based on all the different clusters formed on the basis of amino acid homology, secondary structures, bioinformatics, and polarity of the D1, D2, and D3 domains of ACE2, final clusters of all nineteen species were devised using the K-means clustering method Figure 13.

**Figure 13.** Schematic representation of a possible set of clusters of transmission of SARS-CoV-2.

In Figure 13, it was found that the cluster-1 (C-1) comprising of *Homo sapiens, Pan troglodyte*, and *Macaca mulatta* were close to cluster-5 (C-5) comprising of *Felis catus* (Cat), *Mesocricetus auratus* (Golden Hamster), *Manis javanica* (Sunda pangolin), *Mustela putorius furo* (Ferret), *Rattus norvegicus* (Rat), and *Rhinolphus ferrumequinum* (Greater horseshoe bat) (Figure 13). This C-5 is also close to cluster-3 (C-3) [*Gallus gallus* (red jungle fowl), *Pelodiscus sinensis* (Chinese shell turtle), *Danio rerio* (zebrafish) and *Salmo salar*], and cluster-4 (C-4) [*Capra hircus* (Goat), *Bos taurus* (Cattle), and *Sus scrofa* (pig)]. C-4 also showed resemblance with cluster-2 (C-2) [*Pteropus alecto*, *Pteropus vampyrus*], and cluster-6 (C-6) that is comprised of *Equus caballus* (horse) only. However, both C-2 and C-6 were also close to each other.

Furthermore, pooled analyses based on the two types of substitutions (one is affecting SARS-CoV-2 transmission (M1), and the other one is SARS-CoV-2 non-affecting transmission(M2)) for all six of the final clusters, which are presented in Table 1.

Based on Table 1, information regarding the number of M1 and M2 substitutions and the intra-species transmission of SARS-CoV-2 were presented as follows:



**Table 1.** M1 and M2 substitutions across nineteen ACE2 receptors.
