This study investigated the presence of respiratory viruses in exhaled breath and coughs of individuals with acute respiratory illnesses and evaluated the effectiveness of surgical face masks in reducing viral transmission. Researchers identified seasonal coronaviruses, influenza viruses, and rhinoviruses in exhaled breath and coughs of children and adults. Surgical face masks significantly reduced the detection of influenza virus RNA in respiratory droplets and coronavirus RNA in aerosols, with a trend toward reduced detection of coronavirus RNA in respiratory droplets. The findings suggest that surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals. Respiratory virus infections cause a range of symptoms collectively referred to as acute respiratory virus illnesses (ARIs), commonly known as the common cold. Although mostly mild, these ARIs can sometimes cause severe disease and death. These viruses spread through direct or indirect contact, respiratory droplets, and fine-particle aerosols. While hand hygiene and face masks are recommended for influenza virus transmission, the relative importance of these modes in other respiratory viruses is not well understood. Similar uncertainties apply to the transmission of COVID-19. The study aimed to explore the importance of respiratory droplet and aerosol transmission routes, focusing on coronaviruses, influenza viruses, and rhinoviruses, by quantifying the amount of respiratory virus in exhaled breath and determining the potential efficacy of surgical face masks in preventing transmission. A total of 246 participants were enrolled, with 122 randomized to not wear a face mask and 124 to wear one. Viral shedding was higher in nasal swabs than in throat swabs for all three viruses. Surgical face masks significantly reduced the detection of coronavirus RNA in aerosols and showed a trend toward reduced detection in respiratory droplets. For influenza virus, face masks reduced the detection of virus in respiratory droplets but not in aerosols. For rhinovirus, there were no significant differences in detection with or without face masks. The study found that aerosol transmission is a potential mode of transmission for coronaviruses, influenza viruses, and rhinoviruses. Surgical masks can effectively reduce the emission of influenza virus particles into the environment in respiratory droplets but not in aerosols. The study also found that there could be considerable heterogeneity in contagiousness among individuals with coronavirus and influenza virus infections. The major limitation of the study was the large proportion of participants with undetectable viral shedding in exhaled breath for each of the viruses studied. The study suggests that surgical face masks could be used by ill individuals to reduce onward transmission. The findings have important implications for the control of COVID-19.This study investigated the presence of respiratory viruses in exhaled breath and coughs of individuals with acute respiratory illnesses and evaluated the effectiveness of surgical face masks in reducing viral transmission. Researchers identified seasonal coronaviruses, influenza viruses, and rhinoviruses in exhaled breath and coughs of children and adults. Surgical face masks significantly reduced the detection of influenza virus RNA in respiratory droplets and coronavirus RNA in aerosols, with a trend toward reduced detection of coronavirus RNA in respiratory droplets. The findings suggest that surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals. Respiratory virus infections cause a range of symptoms collectively referred to as acute respiratory virus illnesses (ARIs), commonly known as the common cold. Although mostly mild, these ARIs can sometimes cause severe disease and death. These viruses spread through direct or indirect contact, respiratory droplets, and fine-particle aerosols. While hand hygiene and face masks are recommended for influenza virus transmission, the relative importance of these modes in other respiratory viruses is not well understood. Similar uncertainties apply to the transmission of COVID-19. The study aimed to explore the importance of respiratory droplet and aerosol transmission routes, focusing on coronaviruses, influenza viruses, and rhinoviruses, by quantifying the amount of respiratory virus in exhaled breath and determining the potential efficacy of surgical face masks in preventing transmission. A total of 246 participants were enrolled, with 122 randomized to not wear a face mask and 124 to wear one. Viral shedding was higher in nasal swabs than in throat swabs for all three viruses. Surgical face masks significantly reduced the detection of coronavirus RNA in aerosols and showed a trend toward reduced detection in respiratory droplets. For influenza virus, face masks reduced the detection of virus in respiratory droplets but not in aerosols. For rhinovirus, there were no significant differences in detection with or without face masks. The study found that aerosol transmission is a potential mode of transmission for coronaviruses, influenza viruses, and rhinoviruses. Surgical masks can effectively reduce the emission of influenza virus particles into the environment in respiratory droplets but not in aerosols. The study also found that there could be considerable heterogeneity in contagiousness among individuals with coronavirus and influenza virus infections. The major limitation of the study was the large proportion of participants with undetectable viral shedding in exhaled breath for each of the viruses studied. The study suggests that surgical face masks could be used by ill individuals to reduce onward transmission. The findings have important implications for the control of COVID-19.