Compellingly high susceptibility of Golden Syrian hamsters to SARS-CoV-2 infection supports recent findings of zoonotic transmission cycle between pet hamsters and humans. High susceptibility of Golden Syrian hamsters to SARS-CoV-2 infection

Golden Syrian hamsters (Mesocricetus auratus) have been established as a small animal research model for human infections with severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) and the associated Coronavirus Disease 19 (COVID-19). Worldwide, millions of Golden Syrian hamsters are also kept as pets and come into very close contact with humans. To determine the minimal infective dose (MID) for this species, which is essential to assess the transmission risk, and to define the optimal infection dose for future experimental studies, we orotracheally inoculated hamsters with SARS-CoV-2 doses ranging from 1*105 TCID50 to 1*10-4 tissue culture infectious dose 50 (TCID50). We monitored the body weight and analyzed virus shedding for up to 10 days. We found that an infection dose of 1*10-3 TCID50 was sufficient to induce virus shedding in infected hamsters at levels up to 102.75 TCID50/ml, which is in the range of the estimated minimal infectious dose for humans. In our experimental setup, the MID was 1*10-3 TCID50. Based on data from our virological and pathological analysis, the optimal infection dose for drug efficacy or vaccine studies was determined as 1*102 TCID50. This extremely high SARS-CoV-2 susceptibility of Golden Syrian hamsters needs to be taken into consideration when assessing the transmission risk between humans and pet Golden Syrian hamsters.