Infectious bronchitis (IB) of chickens is a highly contagious disease characterized by damage of the respiratory system and reproductive organs in young animals caused by a virus of the genus Gamma coronavirus. The condition of the respiratory system caused by the IB virus in chickens has many similarities with the pathology of the respiratory system caused by SARS-CoV-2 in humans. The effectiveness of virucidal drugs (Argovit, Triviron, Ecocid, and lauric acid monoglyceride) was tested on chickens inoculated with a tenfold dose of a vaccine strain based on the attenuated virus H120 against IB of chickens. On the 6th day after inoculation, inflammatory changes in the intestines, lungs, and thymus were observed in the control group. The experimental groups were characterized by less pronounced inflammatory reactions and a lower proportion of thymus and lung probes containing genomic IB virus RNA. Since the virucidal activity of four orally administrated formulations was possible only in the intestine, the experimental data indirectly confirmed the hypothesis of the possibility of the predominant accumulation of coronaviruses in the intestine and subsequent lung damage due to the hematogenous redistribution of viral particles and IBV antigens. It was suggested that other coronaviruses including SARS-CoV-2 can implement a similar mechanism.

Patients with COVID-19 can develop pneumonia, severe symptoms of acute respiratory distress syndrome, and multiple organ failure. Nevertheless, the variety of forms of this disease requires further research on the pathogenesis of this disease. Based on the analysis of published data and original experiments on the concentrations of SARS-CoV-2 in biological fluids of the nasopharynx, lungs, and intestines and using a developed modular model of the virus distribution in human tissue and organs, an assessment of the SARS-CoV-2 reproduction in various compartments of the body is presented. Most of the viral particles can transport to the esophagus from the nasopharynx. The viral particles entering the gastrointestinal tract will obviously be accompanied by the infection of the intestinal epithelium and accumulation of the virus in the intestinal lumen in an amount proportional to their secretory and protein-synthetic activities. The relatively low concentration of SARS-CoV-2 in tissues implies an essential role of transport processes and redistribution of the virus from the nasopharynx and intestines to the lungs. The model simulations also suppose that sanitation of the nasopharynx mucosa at the initial stage of the infectious process has prospects for the use in medical practice.