Study assesses impact of Covid-19 mitigation policies

A study by researchers of the CoVida Network - Science, Information and Solildarity showed that the measures to contain Covid-19 in Brazil have already saved millions of lives, but they are not enough to slow down the spread of the pandemic in Brazil. According to mathematical analysis, even in the states that were stricter in terms of social distancing measures since the beginning of the transmission of the country, this set of actions is still not enough to reduce the rate of transmission of Severe Acute Respiratory Infecction by the new coronavirus (SARS-CoV-2) down to levels considered to be under control. The study also shows the crucial role of population adherence to social distancing rules in the reduction of transmission rates of the new coronavirus.

The analysis were available as pre-print at MedRxIV - which provides quick access to the results, but has not yet been peer reviewed. In the study, the researchers assessed the dynamic of transmission in Brazil’s 27 states and the effects of 547 decrees by state governments relative to social distancing. The results show that states that have intensified social distancing measures over time have had better adhesion rates, such as Ceará, Amapá, Bahia Pernambuco, Acre and Maranhão. In these states, the percentage of the population that remained home ranged from 40 to 60% over time.

The studies show that when a state creates social isolation measures, but then goes flexible and implement softer measures, population adherence tends to fall over time, after the initial interventions. This was the case of the southern state of Santa Catarina: on April 13 shopping malls were allowed to open again and many other reopenings were decreed. At each reopening, adherence rates dropped. The state of Tocantins, however, returned with measures as restrictive as they were in the beginning, and yet adherence was also lower.

The leading researcher of the study, Juliane fonseca, doctor in mathematics at the University of Oporto and post-doctorate student at the Center of Integration of Data and Knowledge for Health (Cidacs/Fiocruz Bahia), says that in states that just maintained their early measures, adhesion was higher and transmission rates were lower than in those that decided to reopen some venues at some point. But the best results were observed in the states that intensified social distancing measures and also adopted even more important measures in their capitals, such as true lockdowns.

Another important finding was that the measures in the capital affected the rest of the states, and the reduction of cases in the capital is reflectec in the remaining territory, with an average interval of 10 days in most states. One of the issues is that, in spite of the restriction measures regarding intercity traffic, such as in the state of Bahia, where the main bus station was shut down, the disease still flows from the capital to the countryside. For all the patterns of action of state governments, the research showed that right on the early days, the population adhered to the measures, but started leaving their homes more as time wore on.

Mathematics emphasize, however, that restricting vehicle circulation and enforcing lockdowns are the measures that yielded the best results. The states whose governments implemented more restricted actions had better adherence results, such as Amapá, Bahia, Ceará, Maranhão and Mato Grosso.  

Smartphone data

To measure adherence, the researchers used databases that employed geomonitoring of 60 million smartphones, showing the time these devices remained within a radius of 450 meters of the location they defined as their residence. These data were made available by Inloco, a technology start-up from the state of Pernambuco, and represents aggregated data, that is, it does not inform the identification of any of the devices in an individual fashion.

With the localization data, adherence rates were observed by comparing with the measures implemented by the states and the transmission rates of the new coronavirus. The analysis showed three patterns of measures adopted in the states over time. A group of states created measures and then relaxed them, but then attempted to restrict again; another group created and maintained their initial measures, such as São Paulo; and others created measures and intensified them, such as Amapá. The latter resulted in higher adherence and in control of disease transmission.

Bahia

In a recent study also pre-printed on MedRxIV (and currently being under the evaluation of revisors), the same group of researchers estimated that since April 22 and health system of the state of Bahia would have collapsed if social distancing measures had not been put into practice. It is estimated that the number of infected people would be 20 times higher and the number of deaths would be 14 times higher if the measures had not been adopted. That is, Bahia would have more than 1 million cases and 22 thousand deaths. “Although this number is considered overestimated, just twice the current number of cases would have been enough to collapse the system”, says researcher Juliane Fonseca, doctor in Mathematics at the University of Oporto and post-doctorate student at the Center of Integration of Data and Knowledge for Health (Cidacs/Fiocruz Bahia).