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In recent weeks, there has been a significant increase in the number of reported cases of Covid-19 and, consequently, in the percentage of deaths that arise in all regions of Brazil, including Santa Catarina. One of the great challenges in the midst of the crisis caused by the rapid expansion of the new coronavirus, generating a strong socioeconomic impact, is to establish joint guidelines on the part of the Union, the States and the municipalities to face it. This effort involves not only government leaders and secretaries, health professionals, and economic-financial analysts, but also scientists with different abilities, such as biochemists, epidemiologists, mathematicians, and physicists.
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These researchers use mathematical models to describe the evolution of epidemics and analyze possible scenarios, in order to help decision-making, such as isolation and social distance. In this context, to add new subsidies, two professors from the Physics Department of the Federal University of Santa Catarina (UFSC), the doctors Jeferson de Lima Tomazelli and Rodrigo Pereira Rocha, decided to study the problem and, based on preliminary analytical calculations, they elaborated a probabilistic model and the computational code that allows simulating the evolution of the Covid-19 pandemic, taking into account of underreporting of cases, as indicated by recent studies.
– Our stochastic model, whose innovative computational architecture fell to Professor Rodrigo Rocha, not only aims to predict the number of new cases each day, based on the adjustment of empirical data, but also to conceive possible scenarios resulting from the organization of the system, Las relationships between individuals and the factors that condition or influence their behavior. It is a complex system, involving public health and state interventions in the social and economic fields, explains Tomazelli, who has a doctorate in theoretical physics from the Institute of Theoretical Physics (IFT / Unesp), with an emphasis on quantum field theory and gravitation. .
Rodrigo Rocha has a PhD in Statistical Physics from UFSC and works in the area of complex systems, at the interface between biology and neuroscience. Based on the simulations carried out, both assess that the release of economic activities in Santa Catarina was rushed and that the state health system is at serious risk of saturation if the criteria to facilitate social isolation are not urgently reviewed, as has been been happening. in regions of the country where the rate of social isolation was low.
They also warn of the lack of transparency in the criteria adopted by the South Carolina government for the liberation of activities and the elaboration of rules of social distance, which contrast with the prohibition of the use of public transport. The two scientists are available to cooperate with government agencies in decision making. Learn more in the following Hangouts interview and by email:
What motivated you, two theoretical physicists, to develop a mathematical model to assess the impacts of the pandemic?
Rodrigo Rocha – What motivated us to study the problem was the observation of technical bulletins on the progress of the pandemic. In our perception as physicists, we note some weaknesses in studies on the evolution of the pandemic. When this was in its initial phase in most countries, as in Brazil about two months ago, some bulletins were limited to adjusting the obsolete data, referring to the number of new daily cases, to curves that could not be extrapolated to the history. future of the pandemic and, therefore, did not serve as a diagnosis of the efficiency of social isolation.
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Others adjusted these data using theoretical models whose predictions depend on the knowledge of the individual transmission rate of covid-19 and the recovery time of infected individuals, which vary according to the characteristics of the population and are difficult to estimate a priori.
Simulations similar to ours did not take into account these characteristics and other important factors. We also decided to better understand the effect of underreporting and how it undermines the reliability of the data published in the daily bulletins. Initially, we examined the models used to describe the evolution of the number of susceptible individuals, infected and recovered during epidemics, in large populations. One is the model released in late March by Imperial College London, which brings a series of data with forecasts on the evolution of the Covid-19 pandemic in several countries, including Brazil.
We are following its real evolution through the data available daily from the sources used in this and other scientific works; In our study, we will also use databases such as those of the IBGE, to simulate scenarios of urban centers in the country and the state of Santa Catarina. When we analyze an epidemic, the diagnosis is generally made a posteriori, when we have a complete picture of the evolution of the disease. In the case of covid19, it is necessary to analyze its evolution in real time.
Jeferson Tomazelli – In my case, I decided to make an incursion into another area, to which I can lend the rigor of the analysis, from the perspective of a theoretical physicist familiar with the construction of mathematical models based on first principles; I have always believed that knowledge has no borders and that Science should strengthen its dialogue with society. Professor Rodrigo and I have the same perception and our association has been extremely fruitful; Although we operate in different areas, in the work we are developing our training is complementary.
We are joining efforts to analyze possible scenarios for the evolution of the Covid-19 pandemic. However, the main challenge is to choose the most appropriate strategy to face it, as the disease progresses in the country and in Santa Catarina. As with the entire scientific community, we have strong reservations about the government’s stance on the worsening situation.
In addition to the research activities dedicated to the Covid-19 study, professors and officials from the health area and other departments, in the different UFSC campuses, have been promoting solidarity actions to serve the population, in addition to seeking new tools for control, prevention and support for the treatment of diseases. Our idea is to add subsidies to studies currently underway in the country and abroad.
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What database are you using to account for the number of infected?
Jeferson Tomazelli – Information on the daily number of new cases and deaths reported in the country is available in the database of the Federal Government’s Ministry of Health and on portals of public universities and research centers.
To take into account the effect of underreporting, we use estimates such as the USP School of Medicine, Ribeirão Preto campus, whose studies show that only 7% of Covid-19 cases are reported in Brazil. We rely on this and other recent statistical analyzes, which take into account various factors, such as the insufficient number of tests carried out in the asymptomatic population and the gap between the clinical diagnoses of new cases and the updating of these databases, which are often performed after patients progress to death.
A small subsampling is sufficient to significantly affect the predictions of the mathematical models that describe the evolution of the pandemic, compromising the analysis of strategies for its control.
Rodrigo Rocha – To quantify this effect, we simulate the stochastic model taking into account an underreporting rate of “s”.
In other words, it only measures the test capacity of the population. Therefore, s = 100% means that no Covid-19 cases are reported, i.e. no tests are performed. On the other hand, s = 0%, means that all the individuals in the population are evaluated every time unit. The figure shows the model predictions for the effect of s on the number of new cases. As illustrated, underreporting of cases has a tragic effect on the perception of the pandemic, as in the case of Brazil.
What is the expected deadline to complete your investigation?
Jeferson Tomazelli – In recent weeks we have made significant progress and we already have preliminary results available, which we intend to publish in scientific journals in the future. All academic research must be done carefully; Due to the fragility of the data, caution is necessary, it is not just about the efficiency of the developed model. The forecast becomes increasingly reliable as empirical data approaches reality, with an acceptable margin of uncertainty.
Our challenge is to incorporate this margin of error into our model so that it offers decision-making scenarios. The model developed is not only intended to predict the number of people infected in the next few days or when there will be a saturation of beds available for patients who use the health system; Through the dynamics resulting from the choice of control parameters, our main objective is to identify plausible scenarios to be considered in state interventions. It is about reconciling policies aimed at public health and the economy, it is not possible to dissociate them; However, it must be emphasized that the right to life is a fundamental guarantee provided in the Federal Constitution of Brazil and that it is up to the State to guarantee compliance.
The model we developed is capable of providing a forecast, within a confidence interval, of costs and benefits in taking measures. Any state intervention, such as the restriction or liberation of economic activities, must be done in a transparent way and this implies the participation of different sectors of society. When the State decides to release certain activities, it is necessary to make public the criteria that guided this decision. For example, if the government releases religious services, it is necessary to know the benefits and risks of such a decision.
Any gradual and segmented release of activities cannot do without this analysis; It is useless to know that beds are available without a projected occupation of them, through concrete data and studies. We are talking about public health, the workforce and this has a direct impact on the economy; it is necessary to ensure that people who will become ill can recover or restructure financially, returning to the productive sector of the economy and the consumer market. The crisis that today affects the entire world population makes it clear that education and public health are not a burden on the State, but rather a heritage.
Rodrigo Rocha – This is precisely the central point of our criticisms, the lack of transparency of the measures adopted at the federal, state and municipal levels, with rare exceptions. When we fit the model parameters to the available data, they provide the answers we seek. Therefore, we have precise, mathematical control through different parameters and how they influence the scenarios that arise from the simulations. When you have access to this information, you can set criteria that support a particular decision, such as quarantine flexibility, which involves a number of factors.
Therefore, taking into account the margin of error, we can analyze alternatives and outline new strategies. All of this can be done. In optimization problems, based on simulations of the evolution of pandemics such as Covid-19, spending on disease prevention and treatment implies benefits for the State, at the expense of losses due to the inhibition of economic activities caused by the Social isolation. For this analysis, it is necessary to have control over the parameters involved in decision making and our model has this characteristic.
It is not enough to estimate whether or not there will be saturation of the medical-hospital health system, depending on the number of beds available in the ICU, before the curve corresponding to the total number of infected individuals is flattened. To choose between one or another strategy, it is necessary to know how many people will be at risk, estimate the number of fatal cases and what this represents for society, from a socioeconomic point of view.
How do you evaluate the launch of activities in Santa Catarina made in the last weeks? Do you think there was precipitation?
Jeferson Tomazelli – yes
The resumption of activities was very hasty, as revealed by the data on the number of new cases of Covid-19 in the State, which have been growing daily after the relaxation of social isolation. In our analyzes, we are not just dealing with statistical data. We have also followed the decrees and ordinances of the state government, which interfere with the forecasts of the models.
On April 1, a strategic plan for the gradual resumption of activities was announced, starting on April 30. However, the government made progress and, since April 13, has been launching activities from various sectors, not only the essential ones, less than two weeks after the release of this generic strategic plan, without consulting the scientific community. .
Before the first ordinance went into effect, scientists were already warning about the risks of these measures; A study by specialists from the UFSC Department of Microbiology, Immunology and Parasitology, with the support of a team of mathematicians and engineers, was sent to the Office of the Chancellor on April 10, criticizing the partial resumption of activities that the government of the state of Santa Catarina would authorize it. When asked about this study, published on the NSC Total news portal, the then health secretary said Santa Catarina worked with the parameters (of the model) at Imperial College.
This statement reveals a deep lack of knowledge about the mentioned model, as well as the content of the scientific bulletin published by the English university. The document, dated March 16, refers to the impact of state interventions to reduce Covid-19 mortality and pressure on the health system, not the strategies that will be adopted to meet these objectives.
On the same date in April, we sent to the Research Pro-Rectory at UFSC our project to analyze the efficiency of contagion control at Covid-19, in response to the call from the Federal Public Ministry, earlier that month.
Rodrigo Rocha – The essential point is to have access to the analyzes that justify the preventive measures adopted by the state government. If a resolution determines that people respect the distance of 1.5 or 2.0 meters between them in a pharmacy line, for example, it is necessary to explain why. There is a whole cultural burden accumulated throughout the history of the fight against epidemics that can be useful at this time.
However, Sars-Cov-2 is a new virus, the transmission process of which is still poorly understood, and not everything we learned from other epidemics, such as SARS in 2002, applies to the Covid-19 pandemic.
The resumption of activities is due to pressure from the economic sector and the population. Jobs were closed and thousands of people were left without income. Public policies were implemented late and the reduction of social isolation resulted in agglomerations, like the ones we observed in downtown Florianópolis after the quarantine was released. This is very worrying.
The state government and city councils did not act in sync and there was not even a debate with the academic community. In the simulations carried out, the interventions correspond to reduction factors applied to social interactions, in percentage terms, setting the basic number of reproduction (R0), related to the rate of transmission of the disease.
Predictions of the number of infected and deaths from Covid-19 were made by country and do not take into account regional aspects, and it is not possible to estimate the saturation of the health system of states and municipalities using the Imperial College model.
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Does your study already allow an estimate of when the saturation of the health system will occur in Santa Catarina or in some cities of the state?
Rodrigo Rocha – We are at a very advanced stage of our studies, but there is still no way to make predictions of this nature, within a statistically acceptable margin of error. We conducted a preliminary survey of data with the World Health Organization (WHO) and IBGE, such as the distribution of the population, the number of beds in the ICU and the number of doctors per thousand inhabitants, in each region of the country, which will be used in our simulations. . However, we can make average estimates without the need for a computational model.
Jeferson Tomazelli –
The data on the number of cases registered daily in Santa Catarina is revealing. If the rate of these new cases continues to increase, as we are observing, the saturation of the health system, sooner or later, will occur in a tragic way, as in other States.
We cannot say that it will happen precisely in a week or a month. At the end of March, when the growth rate was slower and the social isolation rules were stricter, it was estimated that the maximum number of cases would occur until the first week of May, without overloading the health system, but this was not So. has been confirmed
According to the previous forecasts, we must prepare to face the peak in April. That did not happen either. The fact is, history is still being written. I will exemplify. In an optimistic scenario, let’s say Covid-19’s basic R0 reproduction number in our state is close to 2.0; Generally speaking, each infected individual transmits the disease to two other susceptibles, before any infected individual in the population recovers and stops transmitting it.
Based on this information, the most widely used theoretical model in mathematical epidemiology predicts that more than 80% of the population will become infected at the end of the pandemic; at the peak, we will have about 20% of people with the disease in this population. However, depending on the medical-hospital infrastructure, saturation of the health system can occur long before reaching this peak.
If saturation occurs before the rate of new cases begins to decline, the system will be overloaded for longer, as long as demand exceeds the supply of beds, and the effects will be catastrophic. Considering the population of Florianópolis, we would have 100,000 infected at the most critical moment of the epidemic. It is estimated that between 5% and 15% of the total infected with Sars-Cov-2 corresponds to the most severe cases; therefore, at the peak of infection, at least 5,000 people would need medical and hospital care.
One of the government’s criticisms is the lack of transparency in the decisions to release activities in Santa Catarina. Is there a state whose strategic plan can be used as a reference?
Jeferson Tomazelli – Realizing the gravity of the situation, the Goiás State government brought together specialists from different areas to develop a strategic plan, launched on April 19. In the multidisciplinary technical team, in addition to economists and statisticians, there are mathematical epidemiologists from the Federal University of Goiás and this plan contains the model used to support the decisions of the government of that state.
The plan makes projections based on data on the number of new cases registered daily, taking into account estimates of Covid-19’s basic breeding number in Goiás. In these analyzes, they take into account the limitations of the model itself, so that decisions are made. taken with a certain margin of safety.
When it comes to empirical data, such as in a voting intention survey, for example, it is necessary to know the profile of the voters before analyzing this data through statistical methods, so that the forecasts are reliable.
Among the measures that generate more pressure to change in SC is the suspension of public transport. The government claims this means that it increases the risk of contagion. The municipality that has been calling for this change for the longest time is Joinville, whose city council argues that there are 400 buses available, while people have to travel in crowded vans. What would be safer?
Rodrigo Rocha – The State government publishes activities based on the number of beds and data on the evolution of the pandemic; Based on that, he tries to justify his actions, but does not reveal documents about the studies behind these decisions. Unlocking activities and, at the same time, not offering structured services leaves the population in a vulnerable situation.
Where are these studies? What is the criterion that allows people to travel from their homes to work, without making possible the most efficient form of urban transport, the bus? This is another example of a lack of transparency in government actions. We cannot feel safe as long as the studies that promoted decisions related to health, people’s lives and the economy remain confidential.
Studies help us understand these decisions. If the study that led the State of Santa Catarina to suspend public transport were transparent, we could answer your question with greater conviction. But the current situation suggests an inconsistency in the release of activities without the population having access to this transport.
Jeferson Tomazelli – From an epidemiological point of view, the greater the number of people, the greater the risk of contamination by the pathogen. If the means of transport are precarious, the contagion rate increases considerably, due to the reduction of the social distance between susceptible and infected individuals. Commercial relations are not reorganized, based on rules of social distance, without the joint restructuring of the public transport system.
There is an evident inconsistency in the actions of the State, by releasing commercial activities without guaranteeing the safety of the population that depends on this means of transportation to travel from home to school and work. The Federal Government and the Government of Santa Catarina have made available budget values and the execution of expenses related to the Covid-19 pandemic through the transparency portals of their General Controllers.
However, there are no technical reports from which criteria are established to control isolation and social distance. This information cannot be withheld from the population.
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