meme and epidemiology

In these quarantine weeks, many people became curious, among many topics, of epidemiological aspects highly linked to the event that was affecting everyone’s daily life. One element that has become very popular is the R0 index, the basic reproduction number. We dealt with this parameter many times, we know it represents a measure of the "speed" with which an infectious disease initially progresses. R0 is characteristic of the epidemic in its initial phase, then to understand if any containment measures take effect, the actual reproduction number is considered, which is usually indicated with R(t), as it refers to a generic day "t". We can say that the link between the two parameters is: R0 = R (0), that is, the basic reproduction number coincides with the actual reproduction number on day t = 0 of the beginning of the epidemic. We know that over time, R(t) represents the average number of people who are infected by an already infected person during the virus infectivity period. In general, R(t) depends on three quantities: on the probability of contagion (P), on the duration of the average period of infectivity (D), and on the average number of contacts of the individuals concerned (C), according to a simple multiplicative relationship.

For example, if R(t) = 2, we have a situation in which each infected person infects two new individuals and the epidemic progresses rapidly as the group of the infected grows geometrically. On the contrary, if R(t) = 0.5, we have a situation in which only one of two already infected individuals manages to infect another individual, the epidemic disappears naturally because at each cycle of infectivity the number of infected individuals is halved. These relationships are very easy to understand and simple enough to illustrate. In this sense, it is really embarrassing to record that people responsible for the highest levels of public health, as is a regional health assessor, can make mystifying statements like

"Does the index at 0.51 mean? that to infect me you have to find two people at the same time infected because it is at 0.50; and this means that it is not so easy to find two infected people at the same time to infect me. This is the effectiveness of the action and what makes us feel comfortable and confident. "

We always avoided entering the political controversy related to the management of Covid-19, but when Science is distorted to such a point, simply to (falsely) reassure citizenship in the face of an alarming situation, we cannot fail to notice it. However, it must be said that there are many people capable of grasping the irony of the situation, some have said that the commissioner's statements are like saying that” with the birth rate at 0.5% to procreate every woman must have sex with two men at the same time”, or even "Do you know that jock about the guy that since there is a one billion chance that someone gets on a plane with a bomb, the probability that two of them get on that plane with a bomb becomes one in a billion billions and then the guy gets on the plane with a bomb? That guy is Gallera. " In short, in the end we have to thank the Lombardia health assessor, it has been a while since we found such a beautiful meme.