The ruling on attributing illness to an apparent cause and on contagion

Question:
Honorable Shaykh, may Allah preserve you, do some doctors look at a disease and say that it has afflicted you due to a clear cause? Is that considered ignorance, or is it obligatory for you to believe that nothing happens except by the permission of Allah the Exalted and His decree?

Answer:
Allah knows best. Diseases differ; some are contagious by the permission of Allah, and some are accompanied by heredity. All of it is by the permission of Allah, Mighty and Majestic. This does not contradict it. Allah, Exalted and Majestic is He, created this disease and made some of it pass from the sick person to others through contagion or heredity. So this is not considered shirk (associating partners with Allah), nor is it claiming knowledge of the unseen, nor is it similar to that.
The Messenger (peace and blessings be upon him) said, "The worst of the insane is a spark from the mosque," and he said, "There is no inheritance for a madman regarding a mushaf." So contagion exists, but it is not permissible to believe that it spreads by itself; rather, it is by the command of Allah, Glorified and Exalted is He, His qada' wa qadar (divine decree and destiny). People in the jahiliyyah (the pre-Islamic age of ignorance) believed that contagion spreads by itself and did not attribute this to Allah, Glorified and Exalted is He.