QCOSTARICA – “We are experiencing the paradoxical situation of reduction in the number of daily cases at the same time that we have an increase in the contagion rate,” are the words of demographer and public health specialist, Luis Rosero Bixby, from the Central American Population Center of the University of Costa Rica (CCP-UCR).
How is this possible, the situation that the country is experiencing with COVID-19 infections?
For that, we must understand how the rate of infection of the disease works, explained Rosero.
The contagion rate indicator, also called the R rate, tells us how many people, on average, each carrier of the SARS-CoV-2 virus, which causes covid-19, would infect. According to the Universidad Hispanoamericana, this week it is 0.9. According to the CCP-UCR, it is 0.89.
This means that each group of 100 people would infect 90 people in the case of the Hispanoamericana index and 89 in the case of the CCP-UCR.
Ideally, this index should be less than 1, as this is a sign that the rate of new cases is going down. This is the fifth week in a row that this value is below 1.
If the index is higher than 1, the evolution of the disease will have greater speed. With a rate of 1 the infection would remain constant.
On the scales of both research institutes, it is still below 1, but this value has risen in recent days. The CCP-UCR indicator went from 0.8 to 0.89 in the last two weeks.
However, as this number remains below 1, cases continue to decline.
Simply put: a step from 0.8 to 0.89 still tells us that the number of new cases is decreasing, only that today it is at a slower rate than two weeks ago.
“The bad news is its increase of 11% with respect to the corresponding estimate at the end of January (R = 0.8)”, states the CCP-UCR report released this Friday afternoon.
“The good news is that the country is still in favorable territory for R well below unity, an indicator that each new generation of infections is less numerous than the previous one. More precisely, the R = 0.89 indicates a reduction of 11% from one generation to another of infections,” the document cites.
For Rosero, there is no single reason that explains this behavior, however, there are hypotheses. This indicator is very volatile because it depends on the dynamics of people’s movement, so noticeable changes can occur at any time.
“It seems that some of the conditions that led to the fall in the rate of infections in January are dissipating, such as restrictions on movement and assembly, less economic activity typical of the time and cautious behaviors of the population,” emphasizes the specialist.
“It also seems that the ascent will continue in the coming days and could even accelerate with the beginning of face-to-face classes,” he adds.
The contagion rate measures the speed at which this virus is transmitted and that, as a consequence, will have an impact on the growth of the number of cases in the future.
If the incubation time of the virus is taken into account (time that elapses from contact with the virus until the manifestation of symptoms and performance of the test), the infections with which the R calculation is made occurred approximately six days before.
It is important to note that the virus remains the same, so far none of its genetic changes or mutations have made it more aggressive or more lethal, and in Costa Rica, the presence of variants that make its spread easier or faster has not been reported.
The contagion rate is also not directly related to the number of hospitalized or deceased, although the more infections there are, the more possible the complications.
Comparison with other countries
The report compares Costa Rica with other countries in Latin America, Spain, Portugal and the U.S. state of Florida, the latter was considered due to its similar cultural characteristics with the Latin American region.
For this week, almost all countries have their R rate below 1. The countries with the lowest transferability are Portugal, with 0.46, Spain, with 0.65, and Colombia with 0.7.
For their part, the countries where transmission has the highest rate are Paraguay, with 1.11, Cuba, with 1.03, and Peru, with 1.02.
The report notes that, according to the US Centers for Disease Control (CDC), a place is considered to have low transmission when it is below 50 new cases per 100,000 inhabitants each week.
“Costa Rica is, therefore, at a moderate level of transmission, but far from what could be considered low transmission. It will get there when it averages 80 or fewer cases diagnosed per day, something that stopped happening since mid-June,” the document emphasizes.