**1. Introduction**

In the last months of 2019, some viral pneumonia cases were detected in the city of Wuhan in China's Hubei Province. A new type of coronavirus has been identified in the etiology of these cases. The virus has spread rapidly. It has created an epidemic in China. Then it spread all over the world, causing a pandemic that continues today. In February 2020, the World Health Organization identified COVID-19, which means coronavirus 2019 disease [1]. The virus that caused this disease was named SARS-CoV-2. Coronaviruses are enveloped RNA viruses that can also infect many animal species. They also cause mild or severe respiratory infections in humans. Previously, Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and Middle East Respiratory Syndrome Coronavirus (MERS-CoV) infected humans and caused epidemics in 2002 and 2012, respectively [2]. But the pandemic caused by the SARS-CoV-2 virus, which continues today, overwhelmingly outperformed these two viruses both in terms of the number of infected people and their spread around the world, according to the epidemics caused by SARS-CoV and MERS-CoV [3]. As of May 7, 2022, more than 516 million cases have been detected worldwide. More than 6.2 million patients died from this disease.

Some of the patients have the disease asymptomatically, while others have it symptomatically. Clinically objective abnormal findings are detected in some asymptomatic patients. In the study of Hu et al., thoracic tomography was performed on

#### **Figure 1.**

*A 31-year-old male with coronavirus disease 2019 pneumonia. Ground-glass opacities (GGO) and atelectasis.*

patients with asymptomatic infection, and typical ground-glass opacities or patchy shadowing was detected in half of the patients, and atypical imaging abnormalities were detected in 20% (**Figures 1** and **2**), [4]. Some of the asymptomatic patients may become symptomatic over time.

Symptomatic disease can also be examined under three categories: mild illness, severe illness, and critical illness. There is a chance that mild disease accounts for the majority of cases. The incubation period for COVID-19 is within the first 14 days after exposure. In most cases, the disease occurs about 5 days after exposure [5]. Cough, myalgia, and headache are the most commonly reported symptoms in patients with symptomatic COVID-19. There are no specific symptoms to distinguish COVID-19 from other infectious diseases [6]. Symptoms such as fever and cough and parameters such as oxygen saturation and lung auscultation findings are the first and most easily accessible diagnostic information. Such information can be used to categorize COVID-19 disease and to select patients for further diagnostic testing. At
