4.1. The detection of PCV4
After the first report of PCV4 in the Hunan province, China (Zhang et al., 2020), the virus was also detected in other provinces of China (Tian et al., 2020). The presence of PCV4 in different geographic locations implied the active circulation of the virus. However, a preliminary screening failed to detect PCV4 in two European countries (Franzo et al., 2020). With the detection rates of 3.28% in six out of nine provinces in Korea (Figures 1A- 1B), this study provided further evidence for the prevalence of PCV4 in pigs. Combining the detection results of the first two publications (Tian et al., 2020; Zhang et al., 2020) and this report (Figure 1C), it was noteworthy to observe that PCV4 was present in pigs of all age groups and in both clinically healthy and different clinically diseased pigs. That fact was similar to PCV2 and PCV3 infections which were found in pigs with different clinical presentations (Segales, 2012; Zhai et al., 2017). Further studies are required to elucidate any association with diseases in pigs of this novel PCV4.