I'm not sure I'd advocate quarantining everyone who's been to Africa. I imagine the cost of that would be huge unless you quarantine them in their own home in which case you've got no guarantee they'd adhere to it without some expensive policing. Folks who've been treating ebola victims (in Africa or anywhere else for that matter) seems like an obvious high risk group to me and worth quarantining. I'm sure you could probably identify some other high risk groups as well.