Review on the current status of Syrian hamsters as an animal model for COVID-19 transmission, pathogenesis, treatment and vaccine research

Animal models have historically played a crucial role in understanding emerging infectious diseases and developing preventive measures such as vaccines and therapeutics. With the emergence of the novel coronavirus SARS-CoV-2, the Syrian hamster has emerged as a valuable model for studying COVID-19 transmission, pathogenesis, treatment, and vaccine development. This popularity stems from the Syrian hamster's cellular expression pattern of the virus receptor angiotensin-converting enzyme-2 (ACE-2), which closely resembles that of humans. The Syrian hamster effectively recapitulates key COVID-19 characteristics observed in patients, including ageusia and anosmia resulting from infection of the olfactory epithelium, dysregulated NETosis, and age and sex dependence of lesion severity. However, like any model, Syrian hamsters have limitations. They do not replicate the systemic response seen in humans following SARS-CoV-2 infection and cannot model asymptomatic courses with silent seroconversion, extrapulmonary multi-organ vascular lesions and thromboses, or neuroinvasion and encephalitis. Despite these limitations, young Syrian hamsters are suitable models for moderate, less therapeutically relevant courses of COVID-19, while older Syrian hamsters represent a useful model for elderly or otherwise predisposed COVID-19 patients.