Coronavirus (Covid-19)

Coronaviruses are named after the Latin word corona, which means crown, because when they are viewed with an electron microscope, they had a round shaped with protruding crown.

Many other coronaviruses from the coronavirus family cause milder diseases with milder symptoms than the new coronavirus. Therefore, coronaviruses have not caused any panic when it comes to diseases such as the common cold. This is why the Covid-19 disease is called the New Coronavirus. The virus, previously called SARS, is also called SARS-CoV-2 because it is a disease very similar to today's new coronavirus.

The Novel Coronavirus Disease (COVID-19) is a virus that was first identified on January 13, 2020, as a result of research conducted in a group of patients who developed respiratory symptoms (fever, cough, shortness of breath) in Wuhan Province, China, in late December.

The outbreak was initially detected in those found in the seafood and animal market in this region. Later, it spread from person to person and spread to other cities in Hubei province, especially in Wuhan, other provinces of the People's Republic of China and other world countries. It was declared a global epidemic (Pandemic) by the World Health Organization on March 11, 2020.

What Are the Symptoms of Covid-19?

Symptoms appear after the incubation period, which varies between 2-14 days after being infected with the virus. Among the main symptoms of Covid-19 disease, which has a new symptom day by day, the most common symptoms are known as high fever, headache and dry cough that continue for several days. However, the following symptoms are observed in some patients;

• Shortness of breath,
• cough with phlegm,
• Sore throat,
• not taste,
• no smell,
• Muscle and joint pains,
• nausea or vomiting,
• Anorexia,
• Nasal flow,
• Headache,
• Severe respiratory failure,

Conditions such as kidney failure can be among the symptoms of coronavirus.

Before going to the relevant health institutions, people who show symptoms of coronavirus should take precautions by wearing a mask to avoid infecting the people around them, follow the social distance rules, and then quarantine themselves.

How to Protect Against Covid-19?

Since the virus mainly spreads from person to person, taking very simple but important measures will take great strides towards preventing the disease.

WHO (World Health Organization) gives the following recommendations for protection from the virus:

• Wash your hands – soap or hand sanitizers can kill the virus
  
• Wear a mask when in public and outside.
• Cover your mouth and nose with a tissue when coughing or sneezing, and then wash your hands to prevent the spread of the virus
• Avoid touching your eyes, nose and mouth – if your hands touch an area that has touched the virus, the virus can infect your body
• Stay away from people who are coughing, sneezing, or have a fever – staying 1 meter away helps protect you from airborne viruses

Apart from this, there are other ways of protection recommended by Ministry of Health.

• Due to the high presence of patients, health centers should not be visited if possible, and contact with other patients should be minimized when it is necessary to go to a health institution.
  
• Eating raw or undercooked animal products should be avoided. Well-cooked foods should be preferred.
• Areas of high risk for common infections, such as farms, livestock markets and areas where animals may be slaughtered, should be avoided.
• If any respiratory symptoms occur within 14 days after the trip, the nearest health institution should be applied by wearing a mask, and the doctor should be informed about the travel history.

What is PCR Test?

Polymerase chain reaction (Polymerase Chain Reaction / PCR), also called molecular photocopying, is a laboratory technique used to amplify a desired DNA segment or to produce multiple copies. PCR can convert even one copy of DNA into millions of copies. In order to carry out this copying process in the PCR technique, the reaction must be subjected to a series of temperature changes that are repeated many times.

What Is the PCR Test Used For?

DNA amplified by PCR can be used in many different laboratory fields. The PCR method, which is generally used in medical and biological research, is frequently used in medicine and genetic research, as well as in the diagnosis of genetic diseases.

Apart from these, PCR is a fast and effective method in the diagnosis of infectious diseases caused by bacteria and viruses. These diseases also include Covid-19SARS-CoV-2.

PCR Test for COVID-19

The Covid-19 pandemic has proven once again how important reliable and easily accessible tests are. The tests for the detection of Covid-19 SARS-CoV-2 are basically divided into two, PCR test and Antibody test.

The PCR test detects the presence of antigens in the body, rather than looking at the immune system or antibodies. Thus, it detects viral RNAs in the body before antibodies occur or symptoms of the disease appear. Thanks to this detection, PCR testing can tell early whether someone is carrying this virus.

Demonstration of Covid-19 SARS-CoV-2 RNA in respiratory system samples by real-time reverse transcriptase polymerase chain reaction (RT-PCR) is the gold standard method in confirming the diagnosis of infection.

How is PCR Test Done?

The Covid-19 PCR test, which is performed by healthcare professionals who take appropriate precautions, is performed with samples taken from the patient's nose or throat with special sterilized sticks. These samples are placed in containers containing solutions. Samples that can stay in these containers for 24 hours without spoiling can also be transported to the necessary centers (laboratories) in containers. These samples, which come to the laboratory, are put into the test cartridge with the primers and probes used by the technicians. After this point, several heating and cooling cycles are performed to automatically convert the RNA of the virus into DNA over the samples and to replicate this translated DNA. If the DNA combines with the probes placed at the end of these processes, this result means "positive".

Is the PCR Test Reliable?

The Covid PCR test is the main diagnostic test, and is known as the most reliable test. Thanks to the PCR test, carriers who do not show any signs of the disease can be found and necessary precautions can be taken. Sample collection and proper processing of samples are extremely important to increase the reliability of the PCR test.

Covid-19 Antigen Tests

Antigens are molecules that cause the immune system to initiate reactions when they are administered to the organism and form a complex with the antibodies that emerge as a result of these reactions. Antigens can be microorganisms, as well as molecules that are foreign to the organism, mostly proteins, such as fats, carbohydrates, chemicals, enzymes.

Antigen tests are also tests that look at whether there are proteins of the virus that creates the Covid-19 disease in the patient's body. Although the antigen test gives faster results and is more economical than the PCR test, it is not preferred. Because the result of a negative antigen test is unreliable, and if the healthcare worker thinks that the potential patient has Covid-19, he may order a repeat test or PCR test.

Covid-19 Antibody Test

The Covid-19 Antibody test, also known as a serology test, is an indicator of people's immune system. These people respond to the Covid 19 infection by developing proteins (antibodies) in their blood that can attack the virus, which shows whether Covid-19 has been present in people's bodies before.

In general, two types of serological diagnostic tests are used in the diagnosis of COVID-19: bedside chromatographic tests and tests based on immunoassay methods.

Although they have less sensitivity and specificity than molecular methods, they are easy to use and give results in a shorter time. However, the inability to reproduce the results obtained during their validation in clinical settings and the inconsistency of the results of the tests create serious diagnostic difficulties.

Among the antibody tests used for SARS-CoV-2, distributed by the Ministry of Health in our country, there are tests that show results by showing IgM and IgG as two bands separately, or both together (total antibody) to form a single band.

Since antibody tests cannot be used at an early stage in acute infection and do not affect the duration of treatment, their use in clinical diagnosis is limited. Tests demonstrating antibody responses can be used for retrospective diagnosis in patients with a negative molecular test result for COVID-19 but with strong suspicion of COVID-19 infection, by showing elevation of antibody levels in blood samples taken from patients during the acute and convalescent periods.