The globally prevalent MPXV strain exhibits high airborne and contact transmissibility in black-tailed prairie dogs.

Since 2022, Mpox has persisted globally, and emerging evidence suggests the monkeypox virus (MPXV) may transmit via aerosols or respiratory particles alongside direct contact. Using a black-tailed prairie dog model, this study evaluated the pathogenicity, transmissibility, and respiratory particle shedding of a globally prevalent MPXV Clade IIb strain. Unlike previous studies focusing on the historic Clade IIa strain (MPXV-USA-2003-044), this work provides the first comprehensive characterization of the currently circulating Clade IIb in this model. The strain exhibited high pathogenicity: by 13 days post-infection (dpi), body weight decreased to 93.3% of baseline, and survival was 50% by 15 dpi. Infected animals developed conjunctivitis, oral/nasal purulent discharge, and cutaneous lesions, with nasal wash viral loads peaking at 104.29 PFU/mL at 9-11 dpi. Notably, both direct contact and respiratory particle transmission occurred with 100% efficiency. Direct contact recipients showed weight loss to 86.3% of baseline, 1/3 survival, generalized lesions, and peak nasal wash loads of 104.62 PFU/mL at 16-18 days post-exposure (dpe). Similarly, respiratory particle-exposed animals had a baseline weight of 84.6%, 1/3 survival, systemic lesions, and peak nasal wash loads of 104.82 PFU/mL at 18-20 dpe. Infected prairie dogs continuously shed high MPXV loads in respiratory particles (109.50 copies/PD/h at 13 dpi), predominantly in >7 μm particles (93%-99% of total), which contained infectious virus (103.28 PFU/PD/h at 11 dpi). These findings confirm black-tailed prairie dogs as an ideal MPXV model and highlight the epidemiological importance of airborne transmission, particularly at close range.