Transmissibility of Clade IIb Monkeypox Virus in Young Rabbits.

The monkeypox virus (MPXV) has spread globally, posing a severe challenge to global public health. This study systematically evaluated the aerosol shedding dynamics of the epidemic Clade IIb MPXV strain in infected young rabbits, along with its direct contact and airborne transmission potential among them. We found that young rabbits could be experimentally infected with MPXV, exhibiting distinct pathogenic features and viral shedding patterns. Young rabbits infected with MPXV shed the virus through nasal secretions and exhaled aerosols, peaking at 7 dpi. In total, 89-95.8% of virus-laden respiratory particles had a diameter ≥4.7 μm. Notably, MPXV can be efficiently shed and transferred among young rabbits through direct contact and airborne routes. The nasal secretions and exhaled virus particles from donor rabbits can be contacted or inhaled by recipient rabbits. Large amounts of viral DNA were detected in the nasal wash of rabbits exposed to contact or airborne exposure. Furthermore, virus particles invade the lungs, causing pathological changes and disseminating them to multiple organs. However, no infectious virus was successfully recovered from these recipient rabbits, as their exposed or inhaled MPXV dose might have been below the MPXV's minimum infectious dose for young rabbits. These findings indicate that although the airborne transmissibility of the current MPXV strain is relatively limited, inhalation of viral particles following airborne exposure can still result in bodily damage. Continuous monitoring of MPXV transmissibility and mutation evolution is imperative to prevent efficient respiratory aerosol transmission, which guides global monkeypox prevention and control strategies.