With 17th of Tammuz coming up in a few days, and 9th Av three weeks later, several people have suggested that fasting might be a danger, as it could weaken one’s resistance to the COVID virus. What is the Rav’s ruling in this case for an otherwise healthy person, and for a person with comorbidities? Also, is there a difference between 17th of Tammuz and 9th of Av? Thanking you in advance,

Yaakov