This question, at least for Germany, appears to be answered by a study of the Robert Koch Institute (RKI), the public health institute in Germany. Especially in times where school starts again, the question is: how likely are children to get infected there? What about public transport? Bus, train, tram?
The Robert Koch Institute analyzed data of reported infections between the end of February 2020 until mid-August 2020. The study differentiates between the number of outbreaks per location and the total number of infections originating from a specific location.
Figure 1 shows the number of infections of selected locations. The size of the circle is directly proportional to the number of infections, and the value of blue color (from light to dark) indicates the average number of cases per outbreak. The darker color the higher the risk of spreading the disease from a single location. Comparing infections originating from elderly homes and private households, both with a similar number of total covid-19 cases, the care homes had fewer outbreaks than private households, but a higher number of cases per outbreak (18.2 in care homes vs 3.2 in private households).
Figure 1. Cases of Covid-19 Infections in Germany (February-mid-August, 2020)
Figure 2 shows the number of outbreaks (%) happening at different locations relative to private households (which is set to 100%). Here, it is clear that the majority of identified outbreaks occur in households, followed by care homes for the elderly. However, this figure needs to be placed in perspective as it is important to consider the number of infections per outbreak (Figure 1), which is higher in refugee centers (20.8) and homes for the elderly (18.8) followed by workplace (14.1) and hospitals (10.2). The number of outbreaks traced back to restaurants, education centers and public transport is very low.
Figure 2. Covid-19 outbreaks relative to Private Households (%) (February-mid-August, 2020)
Figure 3 shows the percentage of cases relative to the private household location (set at 100 %). It shows that the percentage of infection on public transport, schools and universities is very low.
Figure 3. Covid-19 cases relative to Private Household (%) (February-mid-August, 2020)
The numbers have to be taken with a pinch of salt for several reasons: First, during the time of the survey, a total of 202225 infections were reported. Only 27% of these could be attributed unequivocally to one location (e.g. household, restaurants, care homes etc.). Therefore, the findings of the study may not provide an accurate picture of where the infections took place. Secondly, it is important to highlight that many of the locations were closed or had a lower number of visitors during most of the survey period (schools, universities, transport). Therefore, the low number of cases at these sites is everything but surprising. It remains to be seen if the number of outbreaks and infections during the second wave, which is starting in Germany (and most countries in Europe), will change since all locations are now open (e.g. hotels, restaurants, schools).
What does become clear from the study is that private gatherings are major contributors to the outbreaks and cases of corona infections.
In any case, wearing a mask and keeping the distance will significantly reduce the risk of spreading the virus. It will be interesting to observe the number of autumn flu-virus infections this year if all of us wear masks. We may actually see much lower numbers.
Stay safe!
