Figure 2. Whole genome–based phylogenetic relationship of porcine respiratory and reproductive syndrome viruses (PRRSVs) LV4.2.1, the prototype of type I (European PRRSV) (shown in green), and VR2332, the standard strain of type II (North American PRRSV) (shown in pink). Three Chinese isolates reported before 2006 (HB-1, HB-2, and CH-1a) are shown in blue. Chinese 2006 PRRSV isolates are shown in purple. Chinese 2007 isolates are shown in black boldface, and a representative of 2007 Vietnamese strains (07QN) is shown in red boldface. The 2007 Vietnamese and Chinese PRRSV isolates are classified into the same subclade of type II, as are all the 2006 Chinese PRRSV strains.