wa alaykum salam, Hazrat Muhadith e Kabir (may Allah Ta'ala protect him) explained this many years ago. Something to do with the classification of diseases. I remember he was explaining these things to Dr Nisar. A doctor of the Islamic Sciences explaining medicine to a medical doctor
Salaam brothers, I read a interesting answer to a question posed to ala hazrat regarding the idea that disease spreads from one person to another etc. ala hazrat wrote that the idea that illness is passed on from one person to the other if he keeps close company it is completely false and has no evidence what so ever. I accepted what the imam has wrote there and then but other brothers have objected to illnesses such as chicken pox etc. please share your views. Wasalaam