A method of preventing transmission of a retrovirus from a mother to her offspring, by administering to the mother a therapeutically effective amount of a composition comprising a Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)-associated endonuclease, and the two or more different multiplex gRNAs, wherein each of the at least two gRNAs is complementary to a different target nucleic acid sequence in a long terminal repeat (LTR) of proviral DNA of the virus that is unique from the genome of the host cell, cleaving a double strand of the proviral DNA at a first target protospacer sequence with the CRISPR-associated endonuclease, cleaving a double strand of the proviral DNA at a second target protospacer sequence with the CRISPR-associated endonuclease, excising an entire HIV-I proviral genome, eradicating the HIV-I proviral DNA from the host cell, and preventing transmission of the proviral DNA to the offspring.