Table 1: Classification of Human Endogenous Retroviruses (HERVs). Adapted from Nelson [4] and Balada [5]

Class I Class II Class III

Group 1: HERV-HF Group 1: HML-1 HERV-L
HERV-H (RTVL-H, RGH) HERV-F HERV-K (HML-1.1)

Group 2: HERV-RW Group 2: HML-2 HERV-S
HERV-W HERV-R (ERV9) HERV-K10 (HERV18)
HERV-P (HuERS-P, HuRRS-P) HERV-K-HTDV

Group 3: HERV-ER1 Group 3: HML-3 HERV-U
HERV-E (4–1, ERVA, NP-2) HERV-K (HML3.1)
51–1 HERV-R (ERV3) RRHERV-1

Group 4 : HERV-T Group 4: HML-4 HERV-U3
HERV-T (S71, CRTK1, CRTK6) HERV-K-T47D

Group 5: HERV-IP Group 5: HML-5
HERV-I (RTVL-I) HERV-K-NMWV2
HERV-IP-T47D (ERV-FTD)

Group 6: HERV-FRD Group 6: HML-6
ERV-FRD HERV-K (HML-6p)

Other: HRES-1 Group 7: HML-7
HERV-K-NMWV7

Group 8: HML-8
HERV-K-NMWV3

Group 9: HML-9
HERV-K-NMWV9

Group 10: HML-10
HERV-KC4