The study of respiratory pathogens has traditionally been performed by examining virus exposure to and infection of respiratory tract tissues. However, these studies typically overlook the role of ocular surfaces, which represent both a potential site of virus replication and a portal of entry for the establishment of a respiratory infection. To model transocular virus entry in a mammalian species, we established a novel inoculation method that delivers an aerosol inoculum exclusively to the ferret ocular surface. Using influenza as a representative respiratory pathogen, we found that both human and avian viruses mounted a productive respiratory infection in ferrets following ocular-only aerosol inoculation, and demonstrated that H5N1 exposure can result in a fatal infection at viral doses below 10 PFU or for as little as 2 minutes of virus exposure. Ferrets inoculated by the ocular aerosol route with avian (H7N7, H7N9) or human (H1N1, H3N2v) viruses were capable of transmitting virus to na?ve animals in direct contact or respiratory droplet models, respectively. Our results reveal that ocular-only exposure to virus-containing aerosols constitutes a valid exposure route for a potentially fatal respiratory infection, even among viruses which do not demonstrate an ocular tropism, underscoring the public health implications of ocular exposure in clinical or occupational health settings.

IMPORTANCE:

In the absence of eye protection, the human ocular surface remains vulnerable to infection with aerosolized respiratory viruses. In this study, we present a way to inoculate laboratory mammals that excludes respiratory exposure, infecting ferrets only by ocular exposure to influenza virus-containing aerosols. This study demonstrates that the use of respiratory protection alone does not fully protect against influenza virus exposure, infection, and severe disease.