The ruling on attributing diseases to contagion and heredity

Question:
Honorable Shaykh, please inform us: Do some doctors look at a disease and say that it has afflicted you due to a cause that is considered permissible, or is it obligatory to believe that nothing happens except by the permission and command of Allah the Exalted?

Answer:
Allah knows best. Diseases differ; some are contagious by the permission of Allah, and some are contracted through heredity, all by the permission of Allah, Mighty and Majestic. This does not negate the fact that Allah, Glorified and Exalted is He, created this disease and made some of it pass from the sick person to others through contagion or heredity. Therefore, this is not considered shirk (associating partners with Allah). If this is established medically and determined medically, this does not equate to shirk or to claiming knowledge of the unseen or the like. The Messenger (peace and blessings be upon him) said, "Flee from the leper as you would flee from a lion," and he said, "Do not lead the sick animal to the healthy one." So contagion exists, but it is not permissible to believe that it spreads by itself; rather, it is by the command of Allah, Exalted is He. The people of the pre-Islamic age of ignorance (jahiliyyah) believed that contagion spreads by itself and did not attribute this to Allah, Exalted is He.