Abstract: Provided herein are compositions, methods, assays, and devices for diagnosing and treating a viral infection in a subject and/or detecting a viral nucleic acid in a sample. In one example, a sample is treated in a first chamber and via a closing or twisting operation, the sample is flowed into a second chamber, where any pathogenic nucleic acid is detected by oligonucleotides that are specific to the pathogen under test. Further, the oligonucleotides comprise are cleavage site for a restriction enzyme in the second chamber, which cleaves oligonucleotide-pathogenic nucleic acid hybrid resulting in the exposure of an enzyme that was being held by the oligonucleotide to its substrate, which generates a colorimetric and/or another visual readout (e.g., foam formation). Further, the methods, device, or kits provided herein can be used to detect SARS-CoV-2 in a saliva sample from a human subject as a rapid in home diagnostic test for COVID-19.