The new Minister of Health, Jan Blatný, significantly entered Friday’s meeting on the extension of the state of emergency due to the coronavirus epidemic. In addition to Prime Minister Andrej Babiš, he defended the government’s position. However, in his speech, the head of health care explained the somewhat untraditional key indicator of the dynamics of the epidemic, which is the reproductive number.
From the very beginning of the coronavirus epidemic, the increase in those infected, the proportion of those infected in the number tested or the number of hospitalizations are closely monitored. However, the dynamics of the epidemic is clearly described by the reproductive number marked “R”. It is its value that indicates whether the epidemic is in decline or, on the contrary, growing. It shows how many infected people infect other people. When tightening or loosening restrictions, one often looks at the number R, the reduction of which is the main goal of the measure.
When the recent Minister of Health Jan Blatný commented on the current state of the coronavirus crisis in the Chamber of Deputies during the negotiations on the extension of the state of emergency until 3 December on Friday morning, he also commented on the reproduction number.
“If we have a thousand infected, the reproductive number will be 1.5, then the number will increase to 1500. So only by 500. If we have a million infected and the reproductive number is only 1.1, the increase will be only one hundred thousand,” he said. at the lectern.
The ministry itself explains the number differently on its website. “The reproductive number (referred to as R) indicates the average number of other people who are directly infected by one infected patient. For example, reproductive number 2 means that one patient directly infects two other people who can further spread the disease,” Blatný said on his website.
“It’s not a major failure”
“If he was on the exam, you wouldn’t fire him right away, but he would tell him that he probably means well, but let him try to explain it better. I don’t think it’s necessary to make a scandal out of it. It’s not a major failure,” he said. his speech was the executive director of the Center for Modeling of Biological and Social Processes, René Levínský, noting that it was only clumsiness and that the new minister understands well what the number R means.
If the reproduction number is 1.5, it means that 1,000 people will infect another 1,500 people. If the minister’s statement before the deputies were to apply – that is, that the number of infected would increase by 500 – it would have to be assumed that the original thousand of those infected had already recovered or died. In such a case, only 1,500 people from the so-called second generation would currently be infected, which would be 500 more than at the beginning. Cumulatively – in total – however, a total of 2,500 people would go through the disease, ie the first thousand plus another 1,500 who became infected from the first group.
“I think he understood that in the next generation there will be 1,500 infected,” Levínský thinks. “If the disease lasted for one day, it would really work like this. It would flip over, as the minister said. I think he understands that. All he wanted to say is that when there are few infected people, so high a number R doesn’t mind that much, because it gets stuck quickly, but when there are a lot of people, even if the number is close to 1. It’s a problem, so it’s a problem, even if it’s under 1. When you have a million infected and in the next generation 900 thousand, so you are still in the same trouble, “explains Levínský.
The mathematician points out that the number R is only a popularization tool to explain the functioning of the spread of the epidemic. “When simulations are made, it is calculated how the state of the infected changes within a certain period. And in them, the number R is not actually worked at all, this is calculated only ex post,” says Levínský.
In general, if the value of R is less than 1, the epidemic is under control. The number of new infections decreases, while at more than 1 their number increases. The reproductive number results from several indicators: the infectivity (infectivity) of the disease itself, the frequency of personal contacts or the time for which the infected person can spread the infection. At present, the reproduction number according to the Institute of Health Information and Statistics is 1.13.
