Host and viral determinants of airborne transmission of SARS-CoV-2 in the Syrian hamster

Abstract

Airborne transmission is one of the major routes contributing to the spread of SARS-CoV-2. Successful aerosol transmission occurs when people release respiratory particles carrying infectious virus in the fine aerosol size range. It remains poorly understood how infection influences the physiological host factors that are integral to this process. Here we assessed the changes in breathing, exhaled droplets, and released virus early after infection with the Alpha and Delta variants in the Syrian hamster. Infection with the two variants led to only nuanced differences in viral tissue titers, disease severity, or shedding magnitude. Both variants led to a short window of detectable virus in the air between 24 h and 48 h, which was poorly reflected by upper respiratory shedding measured in oropharyngeal swabs. The loss of viable air samples coincided with changes in airway constriction as measured by whole body plethysmography, and a decrease of fine aerosols produced in the 1-10 μm aerodynamic diameter range. We found that male sex was associated with greater viral replication in the upper respiratory tract and virus shedding in the air. This coincided with an exhaled particle profile shifted towards smaller droplets, independent of variant. Transmission efficiency of Alpha and Delta did not differ on average but exhibited clear variation among donor individuals, including a superspreading event. Transmission leading to substantial dual infections only occurred when both viruses were shed by the same donor and exposure was prolonged. These findings provide direct experimental evidence that quantitative and qualitative assessment of exhaled aerosols may be critical for understanding the limitations and determinants of efficient airborne transmission, thus allowing us to control the pandemic with non-pharmaceutical interventions.

Subunit vaccine raised against the SARS‐CoV‐2 spike of Delta and Omicron variants

“…Delta and Omicron variants were the most persistent during the pandemic. Port 45 has shown that golden hamsters inoculated with SARS‐CoV‐2 virus maintain a high level of viral transmission during the first 5 days of infection followed by a drop. Throat swabs were harvested and detected on days 2 and 4 postchallenge in the present work.…”

Design and validation of an exposure system for efficient inter-animal SARS-CoV-2 airborne transmission in Syrian hamsters

“…Indeed, SARS-CoV-2 transmission could occur at this distance between Syrian hamsters even within 1 h at a 2:2 ratio (two infected index and two recipient naïve hamsters). Investigators were also able to demonstrate with this system that airborne transmission dynamics and aerosol characteristics (viral load and particle size) were different between SARS-CoV-2 variants and male and female hamsters ( 10 , 18 ). Dowall et al used a set of three cages, each linked through a 130-mm-diameter connector, and reported SARS-CoV-2 RNA shedding in donor and recipient animals.…”

A neonatal mouse model characterizes transmissibility of SARS-CoV-2 variants and reveals a role for ORF8

“…Although these features establish our model as a unique and workable tool for studying SARS-CoV-2 transmission, other animal models, such as hamsters and ferrets, have certain advantages over the limitations of our system. For instance, our transmission model is based on a mixture of droplet and contact transmission [70]; therefore, any variant-intrinsic differences that can be affected by airborne droplet formation and virion stability cannot be studied in our system, as opposed to the hamster model [49, 120]. An additional limitation of our model is the non-physiological expression of hACE2.…”