Sadly empty offer

My poor sister is home with five sick kids.  On top of that, on Monday my brother-in-law wasn't feeling well, either.  I just can't imagine.  I've been wanting to offer to help, but I'm hesitant, as I don't want to get sick.  Yesterday I decided I was going to suck it up and call this morning to offer, but then last night my mom texted me and said "You probably won't want to be around me; I have a fever".  She NEVER gets sick, so if she got this, I know it's HIGHLY contagious.  Ick.  Still wanting to help or at least be an emotional support, I called BBS this afternoon to see how everyone's doing.  I told her about my concerns, and that if Mom got sick I figured I was sure to get it being around them.  BBS seems to think Mom didn't get it from her kids (they hadn't spent as much time together as I'd thought) so I offered any help I could provide, even if it was just to sit with the kids for an hour so BBS could get out of the house.  BBS said "you know, just because Mom didn't get it from us doesn't mean it's not the same thing and it's not super contagious.  So my final offer: "If there's anything you need that doesn't require me to have much contact with your kids, let me know."  I feel so lame not being able to offer more, but I just can't afford to be sick, especially with Christmas right around the corner and being super low on PTO from work.  I am so lucky to love a sister who gets that sometimes wanting to help and actually being able to are two different things!