Well now. This could be another thread. Here is another difference that Holy Orthodoxy has with the RCC. Are you saying that original sin is transmitted like a virus? Are you saying that the Virgin Mary was not born with original sin?
To answer your question original sin is transmitted through our fallen human nature.
St. Paul in several places in his epistles used the the expression the New Adam in reference to Christ. Thus, for example, in writing to the Corinthians, he says, “The first man Adam was made into a living soul; the last Adam into a quickening spirit.” (1 Corinthians 15:45) Christ is then the New Adam. Sin and death came into the world through the first Adam, but abundant restoration came through the New Adam: " . . . as in Adam all die, so also in Christ all shall be made alive."
It may be that the early Fathers of the Church derived their idea of the New Eve from the oral teachings of the Apostles, or it may be that they took up the very open hints in the writings of St. Paul. Certainly it is not hard to see that if there was a New Adam, Christ, to outbalance the old Adam, there should also be a New Eve, Mary, to outbalance the old Eve. For St. Paul said that the Redemption was superabundant: " . . . where sin abounded, grace did more abound."
The Fathers love to on the contrast of Mary and Eve. God made great plans for the first Eve, but she, in her disobedience, blocked the original design of God. God, however, found a remedy that would more than compensate for Eve: in Mary He would have all that He desired and much more.
The possibilities implied in this parallel and contrast are numerous. When God made the first Eve, He created her without any stain of sin on her soul: she was immaculate. Hence we wonder: Does the concept of Mary as the New Eve imply that she, too, was to be conceived immaculate? God had planned that the first Eve should be in the fullest sense “the mother of all the living.” (Genesis 3:20) For she, with Adam, was not only to transmit physical life to all mankind: she, with him, was to hand on also all the other rich gifts of God, including the greatest gift of all, God’s grace. If, then, Mary is the New Eve in a superabundant redemption, is she to become the channel through which all graces will come to men? God had planned that Adam and Eve, if they had been victorious over sin, would also have been victorious over death, so that He would take both their bodies and their souls into Heaven immediately after their stay in this world. Therefore we may also ask whether the New Eve, by virtue of her share in the victory of the New Adam over death and sin, should be taken body and soul into Heaven even before the general resuurection.
It would be difficult for us, merely using our own reasoning powers, to be sure that that such truths as these really are contained in the Father’s concept of a New Eve. We can come to certainty only through the interpetations of the Church, the living guardian and interpreter of the revelation given to us in Scripture and Tradition. For before He died, Our Lord promised, PROMISED MIND YOU, to send the Holy Spirit to the Church: " . . .He will teach you all things, and bring all things to your mind, whatsoever I shall have said to you."