Comparative virology and pathology of Monkeypox virus in Syrian hamsters, C57BL/6, and BALB/c mice: A framework for preclinical model selection.

Monkeypox virus (MPXV), a zoonotic orthopoxvirus, has emerged as a major public health concern following its global spread in 2022. Robust small animal models are urgently needed to investigate MPXV pathogenesis and evaluate medical countermeasures. Here, we systematically compared MPXV infection in Syrian hamsters, C57BL/6 mice, and BALB/c mice following intraperitoneal inoculation. Syrian hamsters displayed the highest susceptibility, with systemic viral dissemination peaking at 2 days post-infection (dpi) and clearance by 12 dpi. Viral burdens were particularly elevated in the spleen and kidneys, correlating with severe histopathological changes. In contrast, C57BL/6 and BALB/c mice exhibited more restricted viral replication, with the kidneys, liver, and spleen serving as major target organs. Across all models, no cutaneous lesions were observed, underscoring the influence of infection route on disease phenotype. Comparative analysis revealed species-specific tissue tropism and clearance kinetics, confirming the Syrian hamster as a permissive model for systemic MPXV disease, while C57BL/6 and BALB/c mice offer complementary value for mechanistic immunology studies. These findings establish a framework for rational selection of small animal models to study MPXV pathogenesis and to evaluate antiviral and vaccine strategies.