"OUCH"

Without any undue waste of time, please contact the airline they were travelling on and do two things...

ONE) Tell them what has happened and that you are concerned, and ask if they've had any other requests for this info, on that particular flight, leave them your contact details.

They'll probably be wary of a lawsuit so put that to rest.

TWO) Im not too sure how you can do this as I'm not an American, but you should advise the CDC of your information and contact details.

Also, it might be a very good idea to suggest that your family members, all now that have been in direct contact, since their return, to place themselves into voluntary quarantine for a few days, get them to talk to their medico's and ask about these suggestions...PLEASE..

sorry, I dont want to over dramatize this but caution is better than the possible conseqences.

Again, I truely hope all will be well.