When admitted to a hospital, patients are required to be tested for both influenza and COVID-19, said Natalya Pshenichnaya, Deputy Director for Clinical and Analytical Work at the Central Research Institute of Epidemiology of Rospotrebnadzor, in an interview. In addition, the professor explained the fundamental difference between the “swine” flu circulating in the last 10 years and the variant of influenza that came this year, and also gave a forecast for the development of the situation with “omicron” and influenza in Russia. — Natalya Yuryevna, now among the respiratory viruses there is a “battle” between the influenza virus and the “omicron”. Is it possible at this stage in the development of the pandemic to distinguish the flu, which has now come to us, from the COVID-19 caused by the “micron” by symptoms?

“Without a test, it is impossible to distinguish influenza in patients from COVID-19. The same temperature is above 38 degrees, the same headache, the same nasal congestion, dry cough, soreness in the oropharynx, severe general weakness, pain in muscles and joints. These infections are very, very similar. But, in general, even before there were no clear criteria by which it would be possible to confidently make a differential diagnosis between influenza, other acute respiratory viral infections and COVID-19.

However, some time ago, with covid, we still focused on the gradual onset of the disease, loss of taste, smell. Of course, these are also non-specific symptoms, but COVID-19 could be more likely to be assumed. And then it was really confirmed with the help of laboratory tests. And now it has become impossible to even guess. In any case, laboratory testing is necessary.

- After all, flu and COVID-19 are treated with different drugs?

- At the outpatient stage, there are drugs that can be used for influenza, COVID-19, and other acute respiratory viral infections. But there are drugs that are not prescribed, for example, to people who are not at risk, with a moderate course of influenza, and are prescribed to patients who are at risk of getting severely ill with the flu, with complications. These drugs do not work against SARS-CoV-2. Therefore, of course, now it is fundamentally important not to self-medicate, but to consult a doctor who will promptly conduct laboratory diagnostics.

- This year came the Hong Kong influenza A (H3N2). Has he been gone for a long time?

- Influenza A (H3N2) has been all the time since 1968, but usually in the background. Over the past 10 years, various variants closely related to the A(H1N1)pdm09 influenza virus strain have dominated more often. It was this strain that caused the so-called swine flu pandemic in 2009, although this is a completely wrong name, since this flu has long been “humanized”. But in the seasons 2016-2017, 2017-2018 and 2018-2019. influenza A(H3N2) virus began to gain momentum and circulated along with influenza A(H1N1)pdm09. And then he again weakened his position in the 2019-2020 season.

- And in 2020, as they say, the flu disappeared altogether?

- This is true. And now 2021 was marked by the return of A (H3N2).

- Is there any fundamental difference between "swine" and Hong Kong flu?

- There is. If the H1N1 influenza virus was able to actively multiply in the lower respiratory tract, that is, in the lungs, and already in the middle of the first week of illness, somewhere on the 3-5th day of illness, the patient could show signs of viral pneumonia, then the H3N2 influenza virus does not is distinguished by this feature. It mainly affects the upper respiratory tract. However, it often develops bacterial complications from the lower respiratory tract, which are already noted at the end of the first - beginning of the second week of the disease.

- And here it is already necessary to give antibiotics, which are generally useless with COVID-19?

- Yes. If a person is ill with COVID-19 even for a week or 10 days, is admitted to a hospital, then doctors say: “No antibiotics are needed.” Indeed, the vast majority of such patients do not have bacterial complications for a long time. With influenza, after 5-7 days of illness, the cough becomes wet, the sputum discharge is purulent, yellow in color, nasal discharge acquires a yellow-green tint. This suggests that a bacterial infection has joined. Therefore, the flu has always been also formidable and dangerous. It just faded into the background due to COVID-19.

So why did the flu disappear in 2020?

- He just apparently “took a vacation”, due to restrictive measures, more thorough than now, compliance with measures of non-specific prevention of respiratory infections. And now we've all relaxed a bit, we've started to get less vaccinations against the flu, and it's back into active circulation. This year, unfortunately, we have 10% less people vaccinated than in 2020.

- So the vaccine works against H3N2, despite the fact that the Hong Kong flu was not expected?- Of course, he was always in the vaccine. The vaccine is working. Even if a vaccinated person becomes infected with a closely related genetic variant of the virus, to the one that is part of the vaccines, at least he will not become seriously ill. As a rule, the strain composition of vaccines matches the circulating strains of viruses, so vaccines protect those who use them from the most adverse effects of the disease.

“There are scientific articles showing that the flu vaccine works just as well against COVID-19, as it trains the immune system. Do you confirm this?

— On this occasion, there are scientific studies that have been published in high-ranking foreign journals. For example, there is a publication by scientists from the Netherlands about healthcare workers who were actively vaccinated against influenza in the 2019-2020 season. and practically did not suffer from covid or were ill in a mild form. This was back in the first wave of the pandemic, when there was no vaccine for COVID-19. There was also a publication by Italian scientists who showed that older people in the northern provinces of Italy who were vaccinated against the flu were significantly less likely to die from COVID-19. Indeed, it appears that the flu vaccine elicits a more balanced immune system response when confronted with SARS-CoV-2, without developing a cytokine storm.

- And how many cases of influenza are there in the country according to the latest data?

- According to the latest data, in the 4th week of the current year, influenza among other respiratory viruses - 15.9%. Epidemic thresholds for the incidence of influenza and SARS were exceeded in 71 subjects.

- If a person is admitted to the hospital with a suspected covid by ambulance, is he tested for there?

- Certainly. Often they make the entire respiratory panel, which is called SARS-screen. And they do a separate test for COVID-19.

— There is a high probability that a person with the flu can be put in a covid ward, since the symptoms are indistinguishable. Will he get co-infected?

- Patients with confirmed influenza will never be admitted to a ward with confirmed COVID-19. For a hospital, this is essential. If the patient has all negative tests, they will also try to put him in a separate room. Chambers are now trying to choose smaller ones, but, of course, not all hospitals can afford it. In hospitals, a distance of at least 1.5 meters is maintained between patients, and disinfection is constantly carried out. That is, the anti-epidemic regime is observed, the risks are minimized.

- Is flu + covid co-infection really more difficult?

- Really. We saw this in the first wave of the pandemic, when influenza viruses were actively circulating in the human population, and then came COVID-19. The Chinese wrote about it, Britain wrote, experts from Italy and the United Arab Emirates. Patients with coinfection die more often. But doctors understand this, so they conduct mandatory testing when they are admitted to a hospital in order to correct treatment in case of co-infection.

— There is a lot of Omicron now, the wave of infection with this strain is going up sharply. What will happen to the flu? Will the number of infected people increase?

All up to a certain limit. There are laws of epidemiology. For example, under these laws, influenza viruses circulate actively in a given locality for about six weeks. Now the incubation period for COVID-19 has been reduced, so I think that the “omicron” wave will be shorter than the previous ones, approaching those of the flu in duration.

“Delta tortured people for almost half a year. How long will omicron torment?

- I think - one and a half to two months. We just have a huge country, there are many regions, so the waves are stretched in time. It may be longer than in other countries. I think that the rise in the incidence of COVID-19 will continue for another two weeks. Further, the numbers will be approximately the same, and the decline will begin. The flu is also actively circulating now. From the moment when it begins to be actively detected, usually 1.5-2 months also pass. However, there are also ups and downs. Let's hope they don't this year.

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