Virologist - about what is really dangerous mutation "covid"

The third, apparently the most powerful, wave of the SARS-CoV-2 coronavirus pandemic was generated by its Indian strain - the “delta” variant, in WHO terminology. it has spread all over the world, crowding out other variants of “covid”. Many experts say that in its properties it differs markedly from other options, moreover, in the “worse” direction for people.

RBC Petersburg asked to talk about the features of the "delta" option of the HEAD of the Yekaterinburg Research Institute of Viral Infections of the State Scientific Center for Virology and Biotechnology "Vector" of Rospotrebnadzor, DOCTOR of Biological Sciences. Alexandra Semyonova (formerly Deputy Head for Innovation at the St. Petersburg Pasteur Research Institute of Epidemiology and Microbiology).

Delta option

- Has sufficient information been accumulated about the delta option?

- Yes, the information collected in different countries is already quite enough. Hundreds of thousands of cases of this variant of coronavirus have been analyzed. We understand its clinical features.

— What are the most important differences for people between this variant and others — Chinese, British, South African, etc.?

- It's more contagious. Due to some mutations in the genome, it is better adapted to penetrate into human cells, it multiplies faster there - it infects a person faster and more abundantly, affects more tissues, including lung tissues. Therefore, it is also more contagious for others - especially for young people, whom it affects more actively than other options.

Are there any differences in symptoms? For example, is the sense of smell lost or retained?

- He is less likely to lose his sense of smell compared to the classic Wuhan variant of the coronavirus. Its symptoms are more reminiscent of the course of the disease from an acute respiratory viral infection - a person has snot flowing more often, a sore throat more often, coughing and sneezing more often.

- Does it have any special consequences, in particular, a high probability of getting seriously ill?

- Since it quickly penetrates down the epithelium of the larynx into the lungs, the clinic of pneumonia develops faster. If the Wuhan version needed 7-11 days for this, then the “delta” copes faster - about 3-5 days, like the flu. The virus follows the path of "ARVI-zation" - it becomes more and more like the causative agent of a respiratory viral infection.

From the point of view of the course of the disease, it (with the timely start of treatment) is no more dangerous than other options. And in general, the process is exactly the same as with other variants of the coronavirus. Although outwardly, it looks more like a severe, acute viral respiratory illness than the Wuhan variant. Due to the greater rate of development of the disease, people from it tend to get sick more severely.

“If the Wuhan version needed 7-11 days for this, then the Delta copes faster - about 3-5 days”

Antibody quality matters

- Do I need to re-build the treatment methodology, the frequency of vaccinations, and select a vaccine for him?

— No, a new technique is not needed. Existing vaccines against it are quite effective - unless, of course, the body gave the right immune response and the person did not stop losing antibodies after vaccination, due to the characteristics of his body. But there are few such people.

True, the minimum titer (the amount of "correct" antibodies) for the "delta" is required higher than for other options. Vaccination usually gives a fairly large titer, much larger than the minimum (usually 20-40 times) and vaccinated it is enough to resist the "delta".

For survivors, the situation is more complicated. Formally, they develop antibodies and their total number can be quite large, but they still run a high risk of getting sick again. The reason is that their antibodies are often “not perfect”. The vaccine stimulates the formation of antibodies that attack the virus in its vulnerable places, and in those who have been ill, a large proportion of antibodies are not fatal to the virus. Such antibodies can make a big contribution to the total number, but they are useless in the fight against the virus. Therefore, a large number of antibodies does not protect a person from re-illness if these antibodies appeared as a result of an illness, especially if he was ill with previous versions of covid (Wuhan, English alpha, South African beta). "Delta" is more aggressive - and immunity, developed after being ill with other variants of the coronavirus may not protect. Therefore, those who have been ill must be vaccinated six months after recovery.

"Delta" is more aggressive - and the immunity developed after the disease with other variants of the coronavirus may not protect.

What explains the current sharp increase in mortality?

- The surge in mortality is explained precisely by the fact that the "delta" began to affect those who were ill in the first place, among those who were vaccinated - the number of cases is much less. Of course, it also affects those who have not been ill and have not been vaccinated. Most of these people are in the southern countries - in India, Pakistan, etc., due to the peculiarities of the local healthcare system (delayed hospitalization, poor morbidity control, etc.).

In RUSSIA, the proportion of those vaccinated is also small, so we also set records for deaths. The immunity of those who have been ill does not help - their lungs are damaged, antibodies are not always effective, so they get sick again and contribute to record numbers of deaths. In addition, June turned out to be very hot, people took to the streets and actively communicate, often without wearing masks and not keeping their distance. If, for example, it rained and restrictive measures were observed, people would sit at home - and there would be fewer infections, as well as deaths.

Instead of new measures, implement the old ones

- Do you need special methods of protection for the "delta"? Is it transmitted more than other variants during physical contact?

- No, it is transmitted through physical contacts in almost the same way as other options. Special, new, protection measures are also not needed - the existing ones are enough. They just need to be applied. Therefore, for example, I myself have just been revaccinated - six months have passed since my serious illness, and I don’t want to suffer so much for the second time. At the same time, I had a lot of antibodies, but they may be of poor quality, because they appeared as a result of an illness, and not vaccination.

“I myself have just been revaccinated - six months have passed since my serious illness and the second time I don’t want to suffer like this”

- How much did the "delta" squeeze out other options?

- It is more aggressive, more efficient, and therefore, as a result of natural selection, it is crowding out other options all over the world.

- Is the subspecies "delta plus" (Nepalese version) reported by the Ministry of HEALTH very different from the "delta"?

— No, not much. It is still a little more efficient, but fundamentally it does not differ from the “delta”.

Avoid an endless pandemic

- Is there any pattern in the emergence of new variants of coronavirus? For example, do some properties increase in them, for example, infectivity or lethality?

The coronavirus is constantly mutating. The process of mutations goes in the direction of increasing infectivity - each next option is more effective than the previous one. This is the law of natural selection.

— Do new variants increase resistance to vaccines?

Not yet, fortunately. But sooner or later, of course, it will happen.

- And then you have to create new vaccines?

- Oh sure.

— How to avoid the endless SARS-CoV-2 pandemic?

“We need to create an obstacle for new mutations. To do this, it is necessary to minimize the ability of the virus to multiply - that is, the number of sick people. There are two options here. One is the complete self-isolation of all people on earth. Since this is unrealistic, the only option left is total vaccination. Only she is able to interrupt the evolutionary chain of the virus. Otherwise, the pandemic will become endless.