Various measures are being undertaken all over the world to control the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Artificial respirators and extracorporeal membrane oxygenators (ECMO) have been introduced for severely ill patients, and antiviral pharmacotherapy has been attempted. However, in the current situation, it is not feasible to wait for evidence-based effective treatments, and it is imperative to deal with daily situations. It would be very helpful to retrospectively evaluate the doctors who worked during the Spanish flu pandemic without access to medical devices such as ventilators, or drugs including antibacterial and antiviral agents. Based on the fact that Kampo medicine was used to treat patients with the Spanish flu, this article demonstrates the high pathogenicity of the Spanish flu virus, the mechanism of action of antiviral drugs, and clinical evidence. As one of the measures against the COVID-19 pandemic, we propose the role of Kampo medicine, which has relative clinical safety with few side effects, and can be expected to induce antiviral action by autoimmune activation.