It is believed that SARS-CoV-2-laden aerosols are one of the key contributing factors to the spread of the coronavirus pandemic. The Federal Ministry of Health’s decision to add an L for Lüften (ventilation or airing) to its AHA policy (AHA+L) of maintaining distance, regularly washing hands thoroughly and wearing a community mask, shows the importance of airing and ventilating rooms as a preventative measure. With the support of the Robert Koch Institute, the Charité and one of Berlin's local health authorities, Professor Dr. Martin Kriegel, head of the Hermann-Rietschel-Institut at TU Berlin (HRI), has now developed a computational model for predicting the potential risk of infection via aerosol transmission in enclosed spaces. This makes it possible to take appropriate preventative decisions regarding how best to ventilate a space, the number of people permitted in a space at the same time and the length of time they spend there.
We do not yet know how many viruses capable of reproduction an aerosol particle contains and how many you have to breathe in to become infected with COVID-19. This data is hard to obtain and the research is not yet complete, even for other infectious illnesses such as the flu. From a medical perspective, there is still some uncertainty regarding the assessment of a risk of infection with SARS-CoV-2. However, it is essential to contain the spread of the virus and develop effective preventative measures during a pandemic.
Based on our current understanding of SARS-CoV-2 and a retrospective review of 12 small to major outbreaks in Germany and other countries, Martin Kriegel and his team have developed a model to predict the potential risk of infection via aerosol transmission. They were supported in their work by the Robert Koch Institute,the Charité and one of Berlin’s local health authorities.
"Our model has provided four key findings: Firstly, introducing virus-free air into a space greatly reduces the risk of infection. Secondly, the amount of time an infected person spends together with non-infected persons has a decisive impact on the likelihood of infection. This is also true for rooms that are well aired or where the air in the room is filtered,” says Martin Kriegel.
“The third point is that limiting the number of contacts is a very effective way to contain the pandemic. Finally, adopting all of these measures minimizes the rate of transmission via aerosol particles.”
To make this new model accessible to the public, the HRI worked together with Professor Dr. David Bermbach of the Mobile Cloud Computing Research Group at TU Berlin to develop a website providing a simplified estimate of the risk of infection via aerosol transmission in a particular situation based on simple data such as the size of the room, the number of people present and what they are doing, and the quality of ventilation.