1. A method of assessing infection or risk for an infection with a bacteria or virus, comprising: contacting a first sample comprising monocytes, dendritic cells and/or natural killer cells obtained from a patient with an infection or at risk for infection with an antigen from the bacteria or virus under conditions sufficient to induce cell proliferation by the antigen; contacting a second sample comprising monocytes, dendritic cells and/or natural killer cells obtained from the patient with an infection or at risk for infection with a third-party antigen under conditions sufficient to induce cell proliferation by the third-party antigen not from the bacteria or virus; measuring monocyte, dendritic cell and/or natural killer cell proliferation induced by the antigen from the bacteria or the virus by detecting a plurality of markers in the first sample following contacting the first sample with the antigen from the bacteria or virus, wherein the plurality of markers comprises CD154 and at least one monocyte, dendritic cell and/or natural killer cell marker, respectively; measuring monocyte, dendritic cell and/or natural killer cell proliferation by the third party antigen by detecting a plurality of markers in the second sample following contacting the second sample with the third-party antigen, wherein the plurality of markers comprises CD154 and at least one monocyte, dendritic cell, or natural killer cell marker, respectively comparing monocyte, dendritic cell, and/or natural killer cell proliferation induced by the antigen from the bacterial or the virus in the first sample to monocyte, dendritic cell, and/or natural killer cell proliferation induced by viable third-party antigen in the second sample, wherein a difference in monocyte, dendritic cell, and/or natural killer cell proliferation in the first sample as compared to the second sample indicates that the patient has the infection or is at risk for the infection.