Contents
Quick reference
If animals became the source of the first infections, then since the beginning of the epidemic, not a single case of transmission of the virus from an animal to a person has been recorded. Now the source of infection is the person himself, while the infection spreads very quickly.
Basically, the virus is transmitted by airborne droplets and is released when coughing, sneezing and even talking at a distance of less than 2 meters. You can also become infected by contact with a handshake, kiss or hug, as well as touching infected objects.
First, the coronavirus infects the mucous membrane of the nasopharynx. Therefore, to diagnose coronavirus in people, doctors take swabs from the throat and nose. If COVID-19 has already affected the lower respiratory tract, in a hospital setting, sputum can be collected from the lungs and bronchi for diagnosis.
Diagnosis of COVID-19: it was and it has become
From the very beginning of the epidemic, active work has been carried out to create reliable diagnostic methods. Today, the diagnosis of coronavirus allows you to identify the infection at the earliest stages of the disease.
The asymptomatic carriage of the virus was known almost from the very beginning. These are cases where the concentration of the virus is so low that there are no symptoms. At the same time, the person himself poses a threat to others, since he can become a source of infection.
To identify asymptomatic cases of carriage, highly sensitive diagnostic methods have been created that make it possible to “find” the virus even in a minimal amount. And today, tests are carried out even before the first symptoms appear, subject to contact with sick people.1.
Diagnosis of COVID-19
Laboratory diagnosis of coronavirus infection allows you to detect the virus itself, confirm the fact of the infection, and also determine the attachment of a secondary infection, the appearance of thrombosis, etc.
To detect the virus in the body, a swab is taken from the nasopharynx and oropharynx for subsequent study of the biomaterial.
PCR Method for SARS-CoV-2 RNA Detection
This method is from molecular biology. With its help, it is possible to “isolate” the DNA of the coronavirus – the genetic material that is inside the cells.2.
Since the virus is not able to multiply outside the cells, their shell is chemically destroyed and RNA fragments are released. The desired fragment is then copied and expanded by comparing it with a specific COVID-19 RNA. If a match is found, then there is a virus in the test sample. According to the SSC “Vector”, which developed the Russian test system, a false positive result of the analysis is impossible. But there is a possibility of a false negative result, so the rapid test is repeated.
An express test takes from 1 to 6 hours, not counting the time for the delivery of the material to the laboratory. The result is already known within a day.
PCR tests detect the fact of infection with the Sars-CoV-2 virus and determine any of the currently existing strains.
It should be noted that since April 1, the PCR test has been canceled for those who return from abroad by land. For those traveling by plane, upon arrival in Russia, you will need a PCR test, a vaccination certificate or a document confirming that you have had COVID-19
Express diagnostics: detection of antibodies
This diagnostic method works according to a different principle: they look for antibodies in the sample that the body secretes in response to infection with a virus. This analysis takes less than half an hour. The presence of antibodies means that a person is either sick now or has recently had coronavirus. The immune response is formed in about two weeks.
Of interest is the determination of antibodies of the class IgM, IgG to SARS-CoV-2 in the blood. This is a qualitative analysis, that is, it is possible to determine whether or not there are antibodies, as well as a quantitative one – how many of them. But the results are always interpreted as qualitative: “found” or “not found”.
Modern test systems can detect coronavirus caused by any known strains.
Quantitative test for IgG to SARS-COV-2 to assess immunity after illness or vaccination
This test is performed to detect immunity after an infection, even if it is an asymptomatic form, as well as after vaccination.
Immunoglobulins of class G (IgG) begin to appear in the blood 3-4 weeks after infection and can persist for a long time. Quantitative analysis of IgG to the S-protein of the SARS-CoV-2 virus makes it possible to trace the dynamics of the level of antibodies, including after vaccination.
Quantitative test for IgM to SARS-COV
Class M immunoglobulins (IgM) are antibodies that the immune system begins to produce 4 to 6 days after infection with SARS-CoV-2. That is, the presence of these antibodies indicates the presence of infection in the body. It is possible to detect their quantitative level in 1-2 weeks after contact with the pathogen. The level of IgM antibodies can vary individually.
Testing for coronavirus is prescribed for those who can clearly be infected: if they have symptoms, after returning from infected countries or contact with sick people.
– In conditions when, despite all the measures taken, the pandemic does not subside, it is advisable for everyone to conduct a PCR test to determine the infection, and for their own safety. Business trips, vacations in a large crowd of people – all this increases the risk of infection and the development of the disease. At risk are people with existing chronic diseases, as well as those who for some reason have not been vaccinated. You need to think about the fact that no one has yet canceled all other diseases – ordinary pneumonia, heart disease, and so on. These patients also need medical attention and hospitalization,” he said. biotechnologist Denis Yudchits.
If you have returned from a coronavirus-affected country, or if you have symptoms of a coronavirus infection, you need to contact the nearest municipal clinic. If necessary, you will be diagnosed with coronavirus, issued a sick leave or prescribed treatment.
Everyone has the opportunity to diagnose COVID-19, but without a doctor’s prescription, this procedure is paid and is carried out in many private clinics and laboratories. Laboratories use sophisticated equipment. Only those medical institutions that have permission to work with such pathogenic viruses can carry out such tests and diagnostics.
A rapid test for the detection of antibodies of the IgG and IgM class can be bought at a pharmacy and carried out on your own. It costs about 1000 rubles.
Popular questions and answers
Our experts answer popular questions regarding the diagnosis of coronavirus: biotechnologist Denis Yudchits and therapist, rematologist Natalya Karaseva.
Rospotrebnadzor has developed a test that allows you to quickly find out which strain caused the disease in humans. Based on six mutations, the test distinguishes “Omicron” from “Delta” and gives the result a maximum of 5 hours after receiving the sample3.
And Russian scientists have also created a test system that detects a new mutation of the coronavirus – Stealth-omicron (BA.2), which is 30% more infectious than previous strains. The study is also carried out by PCR. The test allows you to distinguish the latest strain from “Omicron” and “Delta”3.
The PCR result can also be false positive. Mucosal cells in different people are updated at different rates. And in some, fragments of an already deceased SARS-Cov-2 may persist in the upper respiratory tract for several weeks.
IgM test results may be negative at the initial stage of SARS-CoV-2 infection. Especially in people with weak immune systems or with concomitant diseases that affect the immune system, as well as if a person is taking medications that depress the immune system. False-positive results of an IgM test can occur in people with autoimmune diseases (thyroiditis, systemic lupus erythematosus).
Sources of:
- Temporary guidelines. Prevention, diagnosis and treatment of a new coronavirus infection. https://library.mededtech.ru/rest/documents/vmr11/
- Polymerase chain reaction (PCR) and its application. Okhapkina S.S., Akishev A.G., Degtyarev S.Kh. http://sciencerussian.sibenzyme.com/papers/popularabout/using-pcr
- Mutations apart: PCR tests have learned to distinguish “Omicron” from “Delta”. Izvestia, January 13, 2022