You can select any INFECTIOUS AGENT affecting humans or animals or both. It can be any pathogen of your interest. You will be needing to discuss the available diagnostic methods in practice and its advantages and drawbacks. Then you have to come up with new assay not neccessarily truly novel but with some major modifications to the existing assays and how this new assay will benefit . Also mention the development of assay from beginning to end like targeting particular gene , designing primers and detection methods, expected outcomes and how it differs from the other methods. Kindly attach the references and discussion. I kindly request you to do in a plagiarism free way. For example for footh and mouth disease , you can say I am designing isothermal amplification over PCR due to these drawbacks . Here is the new workflow for isothermal with a major modification explaining the whole detailed work flow.
