Omicron is the official WHO name for the SARS-CoV-2 B.1.1.529 mutation that causes coronavirus infection. Among the hypotheses of its appearance are changes in the virus in the body of people with immunodeficiency, circulation between the population of animals and humans, insufficient coverage of the population with immunization. The symptoms of omicron are similar to other variants of COVID-19, more often there is an asymptomatic course or a mild disease. For diagnosis, an antigen test, a PCR test, and a CT scan of the chest are performed. Treatment includes a gentle regime and isolation of the patient, symptomatic drugs, antiviral and other etiopathogenetic agents in a hospital setting.
U07.1 COVID-19, virus identified
A new strain of SARS-CoV-2 called “omicron” was registered by WHO on November 26, 2021 on the recommendation of the Technical Advisory Group on the Evolution of Coronavirus (TCGEV). According to the Operational Headquarters for the Fight against Coronavirus Infection, at the beginning of February 2022 in the United States, the omicron strain was detected in all US states. During this period, more than 80% of all patients are carriers of a new variant of coronavirus. At the same time, the more contagious subspecies VA.2 is recorded in 20 states, it occupies up to 3% of all clinical cases of COVID-19.
The omicron strain is a new mutation line in the S-protein SARS-CoV-2 – B.1.1.529 according to the Pango classification, it also includes VA lines.1, VA.2, VA.3. The vast majority of the genetic sequences of the virus detected in patients belong to the subspecies of VA.1. However, since the second half of January 2022, the number of VA mutations has been increasing.2. It has not yet been established exactly why the omicron strain arose. There are four main hypotheses:
- The chronic course of COVID-19. Scientists notice that patients with HIV infection and other forms of immunodeficiency remain carriers of the coronavirus for 6 months or more. Against this background, atypical mutations of the pathogen’s genetic material are possible, which as a result cause the formation of new strains.
- Infection from animals. Some experts note that a new strain of coronavirus could develop in rodents or other animals where it has undergone atypical genome changes. Then the pathogen re-entered the person and continued its circulation in the population.
- Insufficient knowledge of the virus. It is suggested that in countries with a lack of equipment for virus isolation and sequencing, uncontrolled strains and mutations may occur that escape the attention of world science.
- Low level of immunization. The appearance of omicron may be associated with poor organization of vaccination in a number of countries around the world. Specialists in the field of infectology say that favorable conditions are created in the body of unvaccinated people for long-term circulation and changes in the virus.
The first case of variant B.1.1.529 was detected during sequencing of a sample of biomaterial on November 9, 2021 in South Africa. During this period, the third wave of coronavirus infection developed in South Africa, and there was a sharp surge in infections. Then the growth of strain B.1.1.529 was detected in all provinces of the country, after which omicron began to be detected in other states. Most health experts associate the spread of the virus with air travel.
Since the mutation of the virus was first discovered in Botswana and South Africa, experts began to call it “South African”. Later, WHO experts who oppose discrimination against countries and ethnic groups gave the name “omicron” from the Greek alphabet, as for previous versions of the virus. WHO representatives explained that they deliberately omitted the letter “nu”, consonant with the English word “new”, and “xi” – similar in sound to the famous Chinese surname Xi.
There are more than 50 types of point mutations in the omicron genome, which change the well-studied properties of previous strains of the virus and cause an atypical course of COVID-19. The key feature of pathogenesis is high contagiousness. The pathogen spreads 2-4 times faster than the Delta variant, a short contact is enough to infect a person. Family outbreaks are also 3.2 times more likely to be detected if at least one person is infected in the house.
The entrance gate of infection is the epithelium of the upper respiratory tract. At the initial stage, the pathogen penetrates into cells through binding to APF2 receptors, which is controlled by S-protein and transmembrane serine peptidase. With the development of the infectious process, SARS-CoV-2 is capable of affecting type II alveolar cells in the lungs, the epithelium of the stomach and intestines, and vascular endothelium.
At the same time, the growing subspecies VA.2 differs from the classic Omicron strain VA.1 by additional mutations in the spike protein. They help the COVID-19 pathogen to elude the immune response of the patient’s body. It is also assumed that VA.2 has increased virulence. Today, studies of both types of omicron and comparison of their main characteristics are continuing.
Coronavirus infection provoked by a new type of pathogen is characterized by a milder and lighter course. The incubation period for the omicron strain is on average 2-3 days. It is possible that the first signs of malaise may appear the next day after contact with a COVID-19 patient. In many people, infection is asymptomatic, especially in fully vaccinated patients with a sufficient level of immunity.
The typical course of the Omicron strain COVID-19 is close to the classical ARVI. At first, patients complain of moderate headaches, weakness, and body aches. At the same time, the temperature rises within 38 ° C, lasts on average 2-5 days. More than 70% of cases of infection are accompanied by a runny nose, nasal congestion and sneezing, but the ability to sense smells and tastes is partially or completely preserved. Up to 60% of patients experience tickling and sore throat.
A decrease in the sense of smell and taste is observed in a quarter of patients with omicron. Fever over 38 ° C occurs in 30% of patients, the same number of people develop severe chills, increased sweating. Dry cough worries about 40-45% of patients with a new variant of coronavirus infection. In the case of the spread of pathogens to the lung tissue, shortness of breath joins, cough increases, there is a feeling of tightness and pain in the chest.
Current data allow us to call omicron a milder variant of the disease, close to the known types of ARVI that have been circulating in different countries of the world for decades. The mortality rate in European countries is 75% lower than when infected with the delta coronavirus. Intensive therapy is required for 1% of patients, which is 4.3 times less than when infected with other strains.
At the same time, in the statements of the world’s leading infectious disease specialists, there are still great concerns about the situation with omicron. Back in November 2021, WHO experts called the new type “a strain that causes concern.” A short incubation period, high contagion and total infestation of the population can cause the collapse of the healthcare system. The number of infected people doubles in 1.5-2 days, the risk of reinfection is 13%.
After a successful recovery, omicron survivors remain at risk of post-ovoid syndrome, which is diagnosed on average after 3 months. The mechanism of its development involves endothelial dysfunction, autoimmune and neurological components, which is why women are more susceptible to severe residual events after coronavirus.
In a pandemic, all cases of acute respiratory infection are considered suspicious of COVID-19 until proven otherwise. The examination of patients is carried out by family doctors, pediatricians and therapists. In difficult cases, infectious diseases specialists, specialists of the intensive care unit are involved. To confirm the omicron strain, the following types of studies are assigned:
- Direct etiological diagnosis. The “gold standard” for detecting the omicron strain of coronavirus is PCR testing, which has a reliability of over 99%. As an express diagnosis, an immunochromatographic test for the SARS-CoV-2 antigen is performed.
- Indirect etiological diagnosis. A study for antibodies to coronavirus infection is prescribed with a negative result of PCR, if the patient has a typical clinical picture of COVID-19. Immunoglobulins of classes M and G, which reflect the current infection, show the presence of immunity after COVID-19, have diagnostic value.
- General laboratory tests. To assess the patient’s condition and the clinical severity of the disease, a general blood test is used to determine the leukocyte formula, an extended biochemical blood test, a study of acute phase parameters and procalcitonin. Assessment of blood clotting is performed based on the results of a coagulogram.
- Radiation diagnostics. To confirm or exclude inflammatory changes in the lungs, a chest x-ray or computed tomography is indicated. The second method demonstrates high sensitivity in COVID-19, but it is prescribed only for clinical and instrumental signs of respiratory failure.
- Ultrasound of the lungs. Sonography is an alternative imaging method that is performed in addition to computed tomography for confirmed pneumonia. It is informative for determining interstitial changes and consolidations of lung tissue located subpleurally.
When making a diagnosis, experts distinguish omicron from other respiratory infections caused by the influenza virus, respiratory syncytial virus, rhinoviruses and metapneumoviruses. With atypical COVID-19, differentiation is carried out with bacterial respiratory diseases, exacerbation of tuberculosis, viral gastroenteritis. In addition to laboratory tests, the collection of epidemiological anamnesis and risk factors is of great importance.
The treatment program for coronavirus infection, including that caused by the omicron strain, is regulated by WHO documents, on the basis of which methodological recommendations are issued in each country. Most patients with the Omicron strain COVID-19 are treated at home under the supervision of a family doctor. The basis of therapy is non-drug measures, such as warm drinking, nasal flushing, regular ventilation and humidification. Patients who live with their family are advised to isolate themselves in a separate room if possible. With a moderate or severe course of the disease , the following groups of drugs are prescribed:
- Etiotropic agents. In the treatment of the omicron strain COVID-19, synthetic antiviral medications are used according to indications. Alpha-interferon preparations, anticovid plasma, and human immunoglobulin are also used.
- Pathogenetic drugs. On an outpatient basis, it is possible to take janus kinase inhibitors, anticoagulants, inhaled forms of GCS. For patients on inpatient treatment, interleukin inhibitors, systemic GCS, IL-6 receptor antagonists are additionally used.
- Symptomatic medications. Taking into account the clinical manifestations of omicron, antipyretic drugs from the NSAID group, nasal decongestants, mucoactive and bronchodilators are prescribed.
- Infusion solutions. Patients with severe COVID-19 are shown intravenous infusion of saline and colloidal solutions under the control of daily diuresis and blood pressure dynamics.
In the case of a decrease in saturation of less than 92%, standard oxygen therapy begins through nasal cannulas or a facial mask to reach a SpO2 level of more than 96%. If such measures are ineffective or in patients with chronic bronchopulmonary pathology, noninvasive pulmonary ventilation is used in BIPAP, S/T, Pressure Support modes. If hypoxemia persists during treatment, they switch to tracheal intubation for ventilation.
Prognosis and prevention
Despite the large number of infections and the ongoing pandemic, there are encouraging expert opinions regarding the omicron strain COVID-19. Against the background of further weakening of virulence, the pathogen SARS-CoV-2 may become one of the usual pathogens that cause seasonal SARS in the population. However, the appearance of new coronavirus mutations with atypical properties that will lead to a deterioration of the epidemic situation is not excluded.
In the situation with the COVID-19 pandemic and the omicron strain, the key role is given to timely, full and total vaccination of as large a percentage of the population as possible, including children and adolescents. People who have had more than 6 months since the two-dose immunization with mRNA vaccines are recommended to get a booster vaccination to strengthen protection against omicron.
The basic anti-epidemic measures limiting the spread of COVID-19 do not lose their relevance. Proper wearing of medical masks or respirators in public places is a strict recommendation of infectious diseases and epidemiologists. Regular washing of hands or treating them with antiseptic, keeping a distance, limiting visits to crowded places are measures of individual prevention, with the help of which each person reduces their risks of getting sick.