Exploring the potential of enterovirus A71 fomite and respiratory transmission in a hamster model.

Enterovirus A71 (EV-A71) is a common pathogen of hand, foot, and mouth disease (HFMD) frequently contracted by young children. The virus commonly transmits by faecal contamination, and possibly through direct or indirect contact via fomite and respiratory routes. Transmission via fomites and the respiratory route via airborne or droplets is not clearly understood. Mouse-adapted EV-A71 (MP4 EV-A71) was used to study the effect of EV-A71 fomite-induced and respiratory transmission in one-week-old hamsters. For fomite transmission, the hamsters were exposed to coins contaminated with 10⁴ 50% tissue culture infectious dose (TCID₅₀) of EV-A71. All hamsters survived, showing self-limiting progression, and no significant loss of weight, but low viral RNA loads were detected in the oral washes and the mother of the exposed hamsters developed low neutralization titers. Despite the low fomite doses, transmission likely occurred in these hamsters. In respiratory transmission using an aerosol test chamber which was placed within the biological safety cabinet, self-limiting progression were seen in contact hamsters exposed to index hamsters orally infected with 10⁴ TCID₅₀ of EV-A71. Index hamsters showed infection and died, but all contact hamsters survived. Computational fluid dynamics analysis showed that the transmission risk of the virus was heavily dependent on the cabinet airflow. Due to the strong convection flow, the exhaled air from the index-infected hamsters were defected, reducing the risk of infection to the contact hamsters. Taken together, our findings suggest that compared to control oral infections, fomites and respiratory transmission is less effective, but could still occur. This first animal model transmission study can be further refined with different virus dosages, exposure time and air flow to study fomite and respiratory transmission of EV-A71 in hamsters.