In COVID-19 children, significant direct correlations were found in most analyses between mRNA levels of single IFN-I ISGs or of IFN-II and its sensitive genes vs. those of HERV-H-pol, HERV-K-pol, HERV-W-pol, SYN1-env, SYN2-env, and MSRV-env (a few examples are illustrated in Figures S1 and S2 added as supplement). Here, SYN2 is linked to COVID-19.