Ultra high affinity antibodies with binding affinities in the range of 10.sup.10 M.sup.-1, and even 10.sup.11 M.sup.-1 are disclosed. Such antibodies include antibodies having novel high affinity complementarity determining regions (CDRs), especially those with framework and constant regions derived from either humans or mice. Methods of preparing and screening such antibodies, as well as methods of using them to prevent and/or treat disease, especially virus-induced diseases, are also disclosed.