Reducing crowds does help!

A study, recently published in the Nature magazine, describes a limited number of places that collect substantial statistics on increase of the Covid-19 cases in the big cities. Limitations on the maximum occupancy in places such as hotels, gyms and restaurants slow down the spread significantly.

The model from the study predicts that a 20% cap of maximum occupancy can reduce the infections by 80% and more.

The model also found significant social inequities in coronavirus infections.

The researchers from the study used cell phone location data to model the potential spread of coronavirus in 10 largest metro areas in the United States, including New York, Philadelphia, Chicago, San Francisco and Atlanta. The data represents 98 million people and their mobility patterns from March to May.

The research team has also examined Covid-19 cases for each area depending on how often people traveled to certain non-residential places of interest. Those places included grocery stores, hotels, fitness centers, cafes and Healthcare offices and restaurants. In result, the study shows that such places of interest generated the most increases in new cases of infection after the reopening. The model has also revealed uneven distribution of infections with 80% of infections happened in smaller size and more crowded places.

The model also predicted that a lower-income individual has a double risk of catching Covid-19 comparing to a higher-income person, explained by how places in those areas tend to be smaller in size, leading to up to 60% increase in crowding and, therefore, increasing the risk of spread.

The model is not a real experiment and the data does not capture some other non-residential places-of interest, such as schools, prisons and nursing homes. More research is needed to assume whether similar outcomes may emerge among other populations and places.

The capacity approach is also a new methodology aimed to study and evaluate different types of reopening strategy.  Decreasing the maximum capacity coupled with other measures, such as limitations over time of visit, may play an even more significant role in reducing the spread.

Generally, the research teams suggest further testing of the model to guide the policies on how to reopen our society safely.