Researchers at the Universidade Estadual Paulista (Unesp) in Araçatuba have developed an application that works as an “accelerometer for covid-19”, that is, it monitors in real time the tendency of accelerating or decelerating the growth of the disease in more than 200 countries and territories. Available free online, the tool loads data from notified cases available on the basis of the European Center for Disease Prevention and Control (ECDC), with daily updates, and applies mathematical modeling techniques to diagnose the current stage of the epidemic in a given location.
“In addition to democratizing access to information, so that everyone can understand what exactly is happening in their city, state or country, the application allows public managers to assess whether a certain measure adopted to contain the contagion of the new coronavirus is or is not taking place. effect ”, says to Agência Fapesp Yuri Tani Utsunomiya, professor of the Graduate Program in Animal Science at the Faculty of Veterinary Medicine of Araçatuba (FMVA-Unesp) and first author of the article that describes the development of the mathematical model, published in the magazine“ Frontiers in Medicine ”.
To explain how an epidemic evolves, Utsunomiya makes an analogy with a car. In the initial phase, the disease progresses slowly and the number of daily cases increases little, as does a car moving under the clutch. The rate of growth is called the incidence and is measured according to the number of new cases per day. The prevalence corresponds to the number of cases accumulated over time, which would be equivalent to the distance traveled by the imaginary car.
Acceleration and braking
“When the accelerator pedal is pressed, the number of cases starts to grow rapidly, as does an accelerated car gaining speed. In this second phase of the epidemic there is an exponential growth in the number of cases. What all countries are looking for is to stop this acceleration and start stopping the disease and, that is to say, they are two different operations. The first is to take your foot off the accelerator pedal so that it drops to zero. When this occurs, the peak incidence is reached. The second operation involves exerting a negative acceleration on the disease [pisar no freio] so that your growth speed slows down to zero. Without speed, the car stops. And that is what we want, that covid-19 stops being disseminated ”, he explains.
Online application helps to evaluate the effectiveness of public policies that aim to contain the spread of the disease. Credit: Unesp
The covid-19 accelerometer allows you to see, in real time, whether a particular country has its foot on the accelerator or the brake – with some degree of inaccuracy in places where there is a lot of underreporting of cases. However, the researcher points out, the transition between the four stages of growth of the epidemic – slow (green), exponential (pink), deceleration (yellow) and stationary (blue) – can occur alternately. That is, even after slowing or even steady growth, the disease can return to the exponential phase if control measures are abandoned. Hence the importance of tools that help in constant monitoring.
“What we noticed with the analysis of more than 200 countries and territories is that effective control measures have a rapid effect on the acceleration curve, long before the actual drop in the number of daily cases. This behavior of the curve is highly relevant for the evaluation of public control policies ”, he says.
Taking as a reference the cases notified by the official health agencies, the application assembles the incidence curves – the one that you want to flatten to avoid the collapse of the health system – and acceleration of growth in real time, in addition to detecting the transitions between the four stages of growth of the epidemic. To make this possible, the researchers used mathematical techniques such as mobile regression and the hidden Markov model.
“We have developed a simple method, but very robust, which, based on data available in national and international banks, generates accurate information about the progress and movement of the epidemic. But these calculations are made from data that depends essentially on diagnosis [testagem]”, Ponders José Fernando Garcia, professor at Unesp in Jaboticabal and co-author of the article.
Although the underreporting of cases is a limiting factor in the model, which can generate some distortion of scale, the epidemiological curves generated tend to maintain contours very close to the real, according to the researchers.
The bad news is that, when analyzing the current Brazilian curves, it is observed that no state has managed to leave the exponential growth phase, even with quarantine. China, by way of comparison, has reached the stage of steady growth with just six weeks of well-done social isolation. They have also managed to reach the stage of stationary growth Australia, New Zealand, Austria and South Korea.
Italy, Spain and Germany are currently in the growth deceleration phase, thanks to the containment measures adopted.
Suppression and mitigation
Utsunomiya divides public policies aimed at containing the spread of the coronavirus into two categories: suppression measures (more intense and severe, designed to cause rapid reversal of epidemic growth, such as lockdown) or mitigation (aimed at reducing contagion, so that growth occurs in a controlled manner, such as using masks and controlling agglomerations).
“In our study it was very clear that suppression measures are extremely effective in combating covid-19. However, they have been criticized for creating social problems and a profound negative effect on the economy. Mitigation measures, on the other hand, have less socioeconomic impact, but are much less efficient. It is very difficult to find a universal solution ”, says Utsunomiya, who was a doctoral and master’s scholarship holder from Fapesp.
According to the researcher, Japan was one of the only countries that managed to slow the growth of new cases only with mitigation measures. “Great care is needed when comparing strategies adopted by different countries, as factors such as health infrastructure, number and frequency of tests, population density and adherence of the population to the recommendations of health agencies can be decisive for the viability of mitigation measures” , he says.