This research was supported by grants from the National Institutes of Health (E.S.B., V.L.M. & H.W.V.), an Abbott Scholar Award (D.W.W.) and a Cancer Research Institute postdoctoral fellowship (E.S.B.).

Author Contributions The original hypothesis of the article was formulated by E.S.B. and H.W.V. E.S.B. and D.W.W performed all experiments except those characterizing Y. pestis infection (J.S.C. and V.L.M.) and WNV infection (M.E. and M.S.D.). K.A.B.-M. made the initial observation of chronic IFNγ secretion during latency. The manuscript was written by E.S.B., D.W.W., and H.W.V. and all authors commented on data and conclusions prior to submission.