Pathogenicity and contact transmissibility of clade IIb MPXV in African dormice

The global outbreak of monkeypox virus (MPXV) in 2022 raised widespread scientific concern regarding potential changes in its biological characteristics. In this study, we conducted research on the pathogenicity and transmissibility of the currently circulating MPXV Clade IIb strain. Dormice were infected via intranasal (I.N.) inoculation with MPXV at three different doses: 10^3.5, 10^4.5 and 10^5.5 TCID₅₀, respectively. Body weight changes, survival rates, viral loads in various tissues, we monitored the pathological changes in lung tissues and evaluated the transmissibility of the virus among dormice through direct contact with infected dormouse mice or exposure to contaminated fomites. The results showed that higher infection doses of MPXV infection in dormice led to more severe the weight loss and mortality rate, broader tissue distribution, and greater viral replication, indicating a positive correlation between MPXV pathogenicity and infection dose. Furthermore, infected dormice successfully transmitted MPXV to co-housed naïve animals, and indirect exposure to contaminated objects also resulted in infection. These findings suggest that MPXV can be transmitted through both direct contact with infected individuals and contaminated surfaces. This study enhances our understanding of the pathogenic and transmission characteristics of the MPXV strain responsible for the 2022 outbreak and provides valuable insights for MPXV prevention and control efforts.