The COVID-19 pandemic has revealed critical knowledge gaps and assumptions concerning how respiratory viruses spread between hosts.

Traditionally thought to be spread mainly through large respiratory droplets produced by the coughs and sneezes of sick individuals, a growing body of evidence indicates that many respiratory pathogens – including SARS-CoV-2– spread through virus-laden microscopic respiratory aerosols.

In this Review, Chia Wang and colleagues discuss the recent research regarding airborne transmission of respiratory viruses and how an improved understanding of aerosol transmission will allow for better-informed controls to reduce and mitigate airborne transmission.

Until recently, most respiratory pathogens were assumed to spread through large droplets expirated from an infectious person or transferred from contaminated surfaces. This understanding has largely guided public health recommendations in mitigating viral spread.

However, several respiratory pathogens, including influenza and the common cold, are also known to spread through infectious respiratory aerosols, which can float and travel in air flows at far greater distances and for much longer, infecting those that inhale them.

According to a growing body of evidence, much of which gained from studying the spread of COVID-19, airborne transmission may be a more dominant mode of respiratory virus transmission than previously thought. Here, Wang et al. highlight how infectious aerosols are generated, travel throughout an environment and deliver their viral payloads to hosts.

The authors also outline ways to mitigate aerosol transmission at long and short ranges, including improvements to ventilation and airflows, air filtration, UV disinfection and personal face mask fit and design.