Figure 4.

Examples of the proposed patterns of IHNV and VHSV spread in Italy. (i) neighboring farms located in the same water system experiencing disease outbreaks caused by genetically related strains (A,B); (ii) genetically diverse viruses in neighboring farms (C,D); and (iii) infection by identical viruses in farms with no connection via water (E). The time period considered is reported for each map. Infected trout farms are represented by dots colored according to the assignment of the IHNV and VHSV strains to the genetic groups identified in the phylogenetic analysis. Non-infected trout farms are designated in black. The number associated to each infected farm corresponds to the isolates reported in Table 2.