Patients are exposed to infectious agents regularly, regardless of their immunologic status. Traditionally clinicians have decided to institute prophylaxis based on epidemiologic factors, skin test (i.e. PPD), or immunologic parameters. A quantitative and specific method that is non-invasive, such as quantitative PCR, would be desirable to more precisely define those who would benefit from prophylaxis. Similarly, when patients develop disease and are being treated, quantitative, non-invasive techniques are needed to assess response to therapy. This project is designed to develop and test quantitative tests using blood, urine, or sputum samples.