Was I wrong to yell at my brother?

Last time in September, he got us all sick with swine flu from college, which we all eventually recovered from. My younger brother was a few feet away from me and he was coughing but didn't cover his mouth. I got mad at him bc he didn't cover his mouth. Was I wrong to do that? My mom says that it's no big deal bc he wasn't even near me. What do you think?