Abnormalities in the structure and function of neural circuits can disrupt normal physiological processes, leading to various disorders, such as Alzheimer’s disease (AD) and Parkinson’s disease (PD), which are closely associated with dysfunctions within brain neural circuits. Elucidating the architecture of these circuits is fundamental for understanding the mechanisms underlying information processing in the brain, facilitating investigations into the pathogenesis of diverse neurological diseases, and providing a theoretical foundation for their prevention, diagnosis, and treatment. Viral tracers have been instrumental in identifying novel neural circuits or revealing new properties of established circuits. Compared with small-molecule compounds and peptide tracers, neurotropic viruses offer several advantages as neural circuit tracers: first, they possess self-replicative capabilities that enable signal amplification; second, they can label both upstream and downstream neurons across synapses; and third, they are capable of delivering foreign genes into neuronal cells. Herpes simplex virus type 1 (HSV-1) stands out as a significant member among neurotropic viruses because of its unique neurotropic characteristics and transneuronal transmission properties, making it an ideal tool for tracing neural circuits.