I think as far as diagnosis for viruses we really need to revamp our diagnostic methods. Like you mentioned that leukocyte to lymphocyte ratio can give you a hint (although variations exist), but I still think more robust confirmations may sometimes be necessary. I say this for two reasons - to control the unwanted use of antibiotics and avoid the rise of antibiotic resistance microbes and two to access the epistemology and if needed provide antiviral therapies for specific viral infections. As of now cheap confirmatory diagnostic solutions are limited. However, this is the problem demanding a solution.