Romans 5:15 tells us that many died because of Adam's trespass. They didn't just die physically; they experienced death (i.e., sickness, disease, lack of any kind, etc.) because of his trespass. The word trespass in Greek is paraptoma. It's two words, para, meaning close beside or an intimate connection, and pipto, meaning to fall away or abandon. Adam's trespass was falling away from or leaving his intimate relationship with his Father. Do not read that with the mindset of separated from God! Adam fell away. Adam was the one who abandoned his intimate connection with His father. He separated himself from the Father. Mankind (born before the cross) through Adam had moved away from what defined them - their identity in God. When Adam abandoned the intimate connection he had with His Father, his legacy to all mankind (from himself to the cross) was death reigning. Because of Adam's transgression, death grabbed the opportunity to dominate mankind.
Romans 5:12 says that it is because of sin that death spread to all men because all sinned.
In other words, physical death AND the attributes of death, sickness, disease, lack, poverty, fear, etc., spread to ALL men. The word spread is dierchomai, meaning to spread as a report.
I Peter 1:18 says, "knowing that you were not redeemed with perishable things like silver or gold from your futile way of life inherited from your fathers." (1 Peter 1:18, NASB).
Peter is telling us that men passed onto future generations, death, and its attributes (i.e., sickness, disease, poverty, lack of any kind, etc.) that they experienced in their own lives. It wasn't a "sin nature" that was passed down. It was their traditions, their unproductive, ineffective, unreal manners of life.
We do the same today. Our grandparents and parents had a disease, so we expect to have it. We reason that it is part of our DNA. Circumstances like poverty, failure, of fear as a way of life, is passed down generation after generation UNTIL someone chooses something else. UNTIL someone decides to think differently than those who came before them! UNTIL someone chooses to expect a different experience in their life, a better experience than what previous generations walked in. We're not talking about generational curses, but a way of thinking or expectations that we pass down.
Death and ALL its effects, such as sickness, disease, lack, and fear, spread from generation to generation as a report. Sin was the cause. But the effect can only exist as long as the cause exists. So, death only exists as long as sin exists.
THE GOOD NEWS - Jesus took away (removed) the sin of the world!!
Sin was the cause and death was the effect... remove the cause and the effects are gone! Death and all of its effects - sickness, disease, lack, etc. ALL defeated!