There is a useful article 'How to Scan and Clean your Android Device from Adware, Virus & Malicious Apps' which also includes instructions for a Nexus 4, located at:-
As I understand it, it's not a virus a scan will detect but an ad that detects you are on a mobile device (I had thought it was android only, so your iphone was news) which hijacks your browser. You only download the virus if you click on it.