Diseases of a spiritual nature.
In truth, the human being is subject to two kinds of diseases. The first is of a material nature, and the second is of a spiritual nature.
In reality, the cause of all diseases is of spiritual origin. And the major cause is forgetting our love relationship with Krishna, God, the Supreme Person.
The material diseases of the spirit soul are those for which karma is the transmitting agent, i.e., which pass from the body which the soul had in its previous life to the one in which it has been reincarnated.
The material body is in reality the prison of the spirit soul. We have forgotten this, but the fetus in the mother's womb, and then at birth, the being suffers. The body is the source of the suffering of the incarnated spiritual being.
The disease that affected our body in our last life, because of our karma and because we did not erase it, will move and will be found in the body that we will have in our next existence. We will find ourselves in a new body affected by the same disease.
This is how we often see babies born with serious diseases, partially paralyzed or even totally degenerative…
God alone controls Everything for us. We are all under his tutelage. Even the material body in which the soul has reincarnated does not belong to him, because property of Lord Krishna. We come into this world with nothing, and it is empty-handed that we will leave it when the time comes. Everything belongs to God. He is not responsible for the misfortunes and sufferings that we endure.
In reality, we ourselves are responsible for the illnesses, misfortunes and sufferings that we endure.
The more wickedness we show, the more we express in thought, word and deed hatred, racism, indifference and cold-heartedness towards those who are different from us, the more the mass of our Harmful acts increase due to the clouding of our mind, and the more we will be led to suffer in our present life, but especially, in our future life.
That's why people sometimes say, “Why this repetition of misfortunes, or what in God's name have I done to suffer so much?”