| Network-level metrics |
| Density |
Number of edges in the observed network relative to the total number of possible edges in a completely connected network |
| Reciprocity |
Proportion of edges showing mutual connections (Measure of the tendency of vertex pairs to form mutual connections between each other) |
| Degree Assortativity |
Quantifies the tendency of individual nodes to connect with other nodes which are similar to themselves in terms of degree centrality |
| Average path length |
Average number of edges that must the traversed to connect any two nodes in the network, without accounting for the temporal dimension of the connections |
| Diameter |
The shortest distance/path length between the two most distant connected nodes in the network ( = the longest of all the calculated path lengths). |
| Clustering coefficient (CC) |
Proportion of pairs of neighbors of a given node which are connected, measures the tendency of the network to cluster |
| Giant strongly connected components (GSCC) |
The largest subset of nodes that are mutually reachable through directed paths |
| Giant strongly connected components (GWCC) |
The largest subset of nodes that are mutually reachable through undirected paths, therefore not accounting for the directionality of connections |
| Node-level metrics |
| In-degree |
Computed accounting for both the number of connections that each node receives in a defined period and the weights of these connections, hence a measure of the potential sources or origins of infection in that range of time |
| Out-degree |
Computed accounting for both the number of connections that each node sends in a defined period and the weights of these connections, and therefore the number of potential destinations of infection in that range of time. |
| Betweenness centrality |
Frequency with which a node is located on the shortest path length between any pairs of nodes, accounting that the connection between nodes might be stronger along paths with more intermediate nodes that are strongly connected than paths with fewer weakly-connected links. In other words, it is a measure of the tendency of connecting nodes which would be otherwise disconnected |
| Eigenvector centrality |
Indirect measure of centrality determined by the centrality scores of the nodes to which the node of interest is connected |
| Key actors |
| Gate-keepers |
Central nodes in terms of their ability to bridge between the functional basis of the network and the wider community of nodes. They are characterized by high betweenness centrality and low eigenvector centrality values |
| Pulse-takers |
Represent the functional basis of the network, are nodes with the shortest paths therefore easy access to other central nodes as well as to the rest of the network. They are characterized by high eigenvector centrality and low betweenness centrality values |
| Dual functionality |
Nodes that fulfil the same bridging role as gate-keepers simultaneously having easy access to all areas of the network. They are characterized by both high eigenvector centrality and betweenness centrality values |
