Are the spouses responsible for the death of the wife's sister's daughter after she contracted chickenpox, which was transmitted to her by their son?

The Shari'ah commanded precaution against infectious diseases and prohibited the mixing of the sick with the healthy, so that one does not contract the disease and then regret, saying: "If only I had done such and such, it would have been thus."

If a child contracted an infectious disease and there was negligence in his interaction with others, leading to the infection and death of a girl, then whoever was negligent must repent to Allah and increase in righteous deeds.

As for the obligation of expiation (kaffarah) or blood money (diyah), some scholars have stated that infection is not considered a cause for compensation, but rather compensation is due if he was placed in a place known to be epidemic.