Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned.” - Romans 5:12
Whatever opinion anyone holds to the contrary, the painful consequences of the sin of disobedience by the first human pair - Adam and Eve - in the Garden of Eden testify to the eternal truth of the word of God contained in the Holy Bible. God had told the man not to eat of the fruit of the knowledge of good and evil, lest he should die. (Genesis 2:16,17). But the devil, in the guise of a snake, disputed the truth of the word of God in the dialogue between him and Eve, Adam's wife. (Genesis 3:1-4, Good News Bible) As a result of this deception, the woman ate of the fruit of the tree and gave to her husband who also ate. (Genesis 3:6) After due process of judgment (Genesis 3:8-13), God Almighty handed down His decision. - Genesis 3:16-19.
And so, right from that time, man has been experiencing illness and pain of different types, and at the end, he dies. This is in accordance with God's righteous judgment because of sin. See Romans 5:12; 6:23; etc. But there is the glorious hope to be set free from sin, pain and death. - Hosea 13:14; Romans 8:18-23; Isaiah 33:24; etc. St. Paul says: “For our light affliction, which is but for a moment, worketh for us a far more exceeding and eternal weight of glory; While we look not at the things which are seen, but at the things which are not seen: for the things which are seen are temporal; but the things which are not seen are eternal.” - 2 Corinthians 4:17-18.