Abstract
The Delta variant of SARS-CoV-2 causes higher viral loads in infected hosts, increasing the risk of close proximity airborne transmission through breathing, speaking and coughing. We performed a Monte Carlo simulation using a social contact network and exponential dose-response model to quantify the close proximity reproduction number of both wild-type SARS-CoV-2 and the Delta variant. We estimate more than twice as many Delta variant cases will reproduce infection in their close proximity contacts (64%) versus the wild-type SARS-CoV-2 (29%). Occupational health guidelines must consider close proximity airborne transmission and recommend improved personal respiratory protection for high-risk workers.
[Display omitted]
•Close proximity airborne transmission may predominate for SARS-CoV-2.•A majority of Delta variant cases will infect someone else, unlike wild-type virus.•The Delta variant overdispersion parameter (k) and R0 are consistent with smallpox.•Room-scale airborne transmission is a significant factor and requires mitigation.•Workers in close proximity to COVID-19 cases require fit-tested respirators.