Regarding the recent Korean Type 1 field viruses (n = 295) isolated in 2013–2016, all of the isolates were classified into subgroups A (n = 274), B (n = 1), and C (n = 20) under subtype 1 (Fig. 2a) with infection prevalence rates of 50.5% (274/542), 0.18% (1/542), and 3.69% (20/542) among ORF5-positive farms, respectively. Here, CWC15 is linked to infection.