Influenza viruses have been proposed to spread through aerosols, but the importance of this mode of transmission between humans is unclear. Now, Yan et al. provide evidence that humans generate infectious aerosols by characterizing the virus in exhaled breath during natural breathing, prompted speech, coughing and sneezing. By analysing paired nasopharyngeal and breath samples from infected individuals, the authors observed that a significant proportion of the infected individuals shed infectious virus in aerosol particles that have the potential to spread by aerosol transmission (≤5 μm). Surprisingly, coughing and sneezing was not necessary for the generation of infectious aerosols, and sneezing did not increase the amount of viral RNA in aerosol particles. The authors argue that these findings could be used to improve models of airborne influenza virus transmission.