University of São Paulo: Mobility data show effectiveness of isolation adopted with low number of covid-infected

For A survey with the participation of the Institute of Mathematics and Statistics (IME) of USP on the measures of social isolation adopted in the covid-19 pandemic used mobility data captured by cell phone to assess the places where this isolation was most effective. The researchers point out that, where mild isolation was adopted, when the number of cases was not high, it was possible to stop the rapid growth of the pandemic, even in a period without vaccines and with crowded hospitals. Soft isolation is when there is no more radical lockdown or back-and-forth control, as occurred in Argentina and Asian countries. The study shows that successful isolation strategies reduced the incidence of the disease from 24% to 40%. For the future, those responsible for the study reinforce the need for reliable mobility data in real time, in order to improve epidemic control strategies.

The research analyzed the impact of social isolation in Brazil on the evolution of the epidemic, during the first wave of covid-19, which took place last year. “Given the diversity of actions, this analysis is very complex”, points out Professor Sérgio Oliva, from IME, one of the researchers who carried out the work , to Jornal da USP . “However, some results stand out, mainly, from the effectiveness of this mild isolation, when applied at the beginning.” The research results are presented in the article A snapshot of a pandemic: The interplay between social isolation and COVID-19 dynamics in Brazil , published Sept. 15 in the scientific journal Patterns , by Cell Press.

The professor explains that, in the pandemic, social isolation was used as a preventive or remedial measure. “The preventive measure is characterized by the application of this mild isolation when the disease was already established, with a minimum number of cases per 100,000 inhabitants, but it had not yet reached a very high threshold, which varies according to the size of the city. This made it possible to mitigate progress, slowing down the growth rate, giving time for the health system to prepare itself”, he reports. “As a remedial measure, isolation occurs when the number of cases has already exceeded a threshold, that is, the number of cases per 100,000 inhabitants is very high, then mild isolation is not enough and more extreme measures, with lockdown , have to be taken.”

Mobile phone mobility data are an indirect measure of the effect of isolation policies, Oliva points out. “As in Brazil there was no strict control of isolation, these measures proved to be one of the only ones available to measure adherence to them”, he observes. “It is important to emphasize that all the information used in the study was provided by a company that collects the data in an aggregated form by cities, therefore, with no impact on individual privacy.”

isolation at the right time

The researchers analyzed the disease incidence and isolation index data from several Brazilian cities, later aggregating them by demographic hierarchy and crossing them with human development index data. “The result is that there is an impact from the mild isolation measures carried out in Brazil. When done at the right time, they mitigated the spread of the disease in an era without vaccines and hospitals were close to collapse. Successful isolation strategies have reduced the incidence of the disease from 24% to 40%”, reports the IME professor.

“Cities that took longer to implement such measures suffered the most from the pandemic,” says Oliva. “The impact and effectiveness of the São Paulo Plan was also verified through the isolation data, delaying the peak of the disease in the cities of the interior.”

“A centralized, permanent and effective crisis monitoring system, with public metrics and the participation of experts from various areas, would feed policy decisions, would provide more transparency and could have made the impact of the epidemic in Brazil lesser”, emphasizes the teacher. “With that, the disease would possibly not have ramified so much and we would have better controlled the pandemic, reducing deaths until the arrival of the vaccine.”

As for the feasibility of using this type of data in the case of future pandemics, the professor points out that each epidemic differs from the previous one, however, the work makes clear the importance of having real-time, reliable and nationwide mobility data without reveal the identity of the people who had the information analyzed, preserving individual privacy. “This allows for a quick prediction of the spread of the epidemic and subsequent optimal control of plans for social distancing, avoiding overloading the health system, possibly without the need to impose very strict mobility restrictions”, he stresses.

“A centralized, permanent and effective crisis monitoring system, with public metrics and the participation of experts from various areas, would feed policy decisions, would provide more transparency and could have made the impact of the epidemic in Brazil lesser”, emphasizes the teacher. “With that, the disease would possibly not have ramified so much and we would have better controlled the pandemic, reducing deaths until the arrival of the vaccine.” In addition to Oliva, the work had the participation of researchers Cláudia Peixoto, Diego Marcondes and Pedro Peixoto, from IME, Mariana Melo, from USP’s Lorena School of Engineering (EEL), and Cláudia Ferreira, from the São Paulo State University (Unesp) in Botucatu.

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