Despite the enormous economic and health-related burdens caused by respiratory infectious diseases globally, there are significant knowledge gaps regarding how these are spread by aerosols. The covid-19 pandemic made it clear that understanding airborne transmission is especially important in healthcare, where workers and patients are highly exposed to sources of virus. This thesis aims to advance the knowledge about airborne transmission of infectious diseases, mainly in hospital settings. More specifically, the objectives were to identify sources and risk factors for airborne virus, evaluate prevention strategies and explore the dynamics of infection via inhalation.

Sara Thuresson will defend her PhD thesis "When the air went viral: Exploring SARS-CoV-2 in aerosols during the covid-19 pandemic".

"In total, we collected over 1100 air samples at hospitals during the covid-19 pandemic, both close to covid-19-patients and in other areas, such as ward corridors. The samples were analysed for SARS-CoV-2 RNA content to investigate presence and risk factors for airborne virus.
Overall, SARS-CoV-2 RNA was detected in around 10% of the samples collected close to patients. In corridors and anterooms, less than 5% of the air samples contained SARS-CoV-2.
A number of factors significantly increased the risk of detecting airborne virus in patient rooms: smaller distance to the patient, lower ventilation rates in the room, and higher viral load of the patient, which correlated with the number of days since symptom onset. 
To further understand aerosol transmission dynamics, we modeled emissions of infectious virus from an individual in a typical
office size room. The simulations showed that a susceptible person can inhale one infectious dose within minutes upon entering a room with an infected individual. 
In conclusion, this work contributes to increased knowledge about sources of airborne virus, risk factors and prevention strategies. Our results support the importance of airborne SARS-CoV-2 in transmission of covid-19, but also highlight the challenges of predicting risk situations and designing effective mitigation strategies. Importantly for indoor environments, the risk of infection is smaller with increased ventilation and distancing to the source. Moreover, transmission dynamics are likely highly dependent on individual variations in viral emissions."

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