The synthetic circuit offers a specific therapeutic function where it works on the modification of gene regulatory pathway. This modification can be performed through molecular regulatory systems by using devices that can sense certain signals (sensors) and then produce an output (effectors or actuators) as a response. Currently, the detection of virus infection is challenged continuously due to conventional methods, which require a trained manpower, high cost of equipment, infrastructure, and reagents. A synthetic regulatory system is designed through the modification of the natural regulatory pathway for easy detection of viruses. Designed systems of genetic circuits include logic gates, toggle switches, oscillators, and biosensors, which play a major role in the detection of virus infections. Recently, developed synthetic circuits such as toehold switches and CRISPR-Cas systems are being used for the identification of Zika virus, SARS-CoV-2, etc. CRISPR-based diagnostics such as SHERLOCK and DETCTR-based tests are used to identify multiple SARS-CoV-2 genes within 30–60 min. These modified genetic circuits facilitate real-time detection, precise response, and prospective therapeutic applications in viral detection.