Airborne disease transmission in a wellmixed room: Airborne transmission rate  Summary and Q&A
TL;DR
Transmission rates and infection quanta determine the rate at which individuals become infected in indoor spaces.
Questions & Answers
Q: How is transmission between an infected person and a susceptible person explained?
Transmission occurs when the susceptible person breathes in infected droplets, and the infectivity of a virion, along with the mask factor, determines the probability of infection.
Q: What determines the number of new infections per time?
The number of new infections per time depends on the transmission rate, beta, which is the rate at which a susceptible person becomes infected, and factors such as the concentration of virions per volume and the flow rate at which the susceptible person samples the air.
Q: What is the role of infectivity and the mask factor in transmission?
Infectivity refers to the probability that an individual virion causes a person to become infected. The mask factor represents the transmission or penetration probability of droplets through a mask and plays a role in reducing transmission rates.
Q: How can the steadystate transmission rate be calculated?
The steadystate transmission rate, termed beta bar, is determined by the steadystate concentrations of virions, which depend on factors such as the production rate, the outdoor airflow rate, and the mask factor.
Summary & Key Takeaways

The concentration of virions in the air per volume, determined by a mass balance in a wellmixed room, leads to the transmission of the virus from an infected person to a susceptible person.

The transmission rate, beta, expresses the rate at which another person may become infected by breathing in infected droplets.

The infectivity of an individual virion, combined with a mask factor, affects the probability that a susceptible person will get infected.