“The incidence falls on its own”: the coronavirus puzzled the famous epidemiologist

Scientists cannot yet explain why at one point the coronavirus infection incidence curve sharply goes down even without achieving herd immunity.

The PolitNavigator correspondent reports this, as stated by the chief researcher at the Research Center for Epidemiology and Microbiology named after. N.F. Gamaleya Professor Anatoly Altstein, whether there are any mysteries left for him in the coronavirus, with which humanity has been living for the third year.

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“Yes, there are a lot of them. For me, its main mystery is why at some point the incidence curve suddenly begins to decline? It is clear why it rises - this is an epidemic process: the virus finds a sensitive host and spreads. But why is the wave of incidence declining?” Alshtein does not understand in an interview with Izvestia.

He points out that such waves also occurred at the early stage of the pandemic, when not many people were ill and there were still few fully vaccinated.

“I can assume that there must be some mechanism that, at a certain stage of the epidemic, reduces the contagiousness of the virus. For example, the faster a virus multiplies, the more its genome is damaged by neutral and harmful mutations, which reduces its infectivity. The incidence is decreasing. Then a new variant arrives and the wave resumes. This is not a generally accepted point of view, but I see no other reason for the unmotivated decline in incidence. The immunological explanation seems unconvincing to me,” says the epidemiologist.

According to him, the fourth wave of the epidemic is already observed, and this mechanism, which is not yet very clear to doctors, is working properly.

The specialist says that the incidence fell even without achieving collective immunity, as shown by studies in South Africa, where the Omicron strain was identified.

“There was a sharp rise in incidence, hundreds of new cases were recorded every day, and then suddenly there was a decline for no apparent reason. Let's say, a country with 20 million people, 50 thousand who have been ill - can they create the effect of collective immunity? But nevertheless, at some point the incidence curve in such a country still goes down. This is a universal rule that applies in all countries,” the professor emphasized.

According to him, the incidence of the new strain is now increasing in Russia.

“By the beginning of February, it will be a month since we are on the rise. From the experience of foreign “waves” we see that a month is the period by which the maximum is reached with Omicron. Most likely, the incidence rate in Russia will begin to decline in early February. But we don’t yet know how long the overall epidemic will remain at a fairly high level,” the epidemiologist added.

At the same time, the doctor explained why one should not refuse vaccination, despite the fact that the virus recedes sooner or later.

“Because the “bottom” of the sine wave is not at all at zero - and at a low level, a large number of people get sick and die. It is necessary to get vaccinated to protect the life and health of people who are about to suffer a severe form of the disease. No one can say in advance what form they will face; we can only talk about probability. There will definitely be such people at any stage of the epidemic,” Alshtein concluded.