Clinical Characteristics of COVID-19 Infection

*Mohamed Abdullah Jaber*

## **Abstract**

The typical clinical symptoms of the patients who suffered from the novel viral pneumonia were fever, cough, and myalgia or fatigue with abnormal chest CT, and the less common symptoms were sputum production, headache, hemoptysis, and diarrhea. This new infectious agent is more likely to affect older males to cause severe respiratory diseases. Major risk factors for severe illness and mortality from COVID-19 are age, comorbidities such as: heart disease, hypertension, prior stroke, diabetes, chronic lung disease, and chronic kidney disease and associated with adverse outcomes. Loss of taste and smell preceding the onset of respiratory symptoms has been reported.

**Keywords:** COVID-19, Clinical, Coronavirus, SARS-CoV

#### **1. Introduction**

This chapter will discuss the clinical features of COVID-19. The epidemiology, virology, prevention, and diagnosis of COVID-19 are discussed elsewhere.

#### **1.1 Asymptomatic infections**

Asymptomatic infections have been well documented. One review estimated that 33 percent of people with SARS-CoV-2 infection never develop symptoms [1]. This estimate was based on four large population-based, cross-sectional surveys, among which the median proportion of individuals who had no symptoms at the time of a positive test was 46 percent (range 43 to 77 percent), and on 14 longitudinal studies, among which a median of 73 percent of initially asymptomatic individuals remained so on follow-up. However, there is still uncertainty around the proportion of asymptomatic infections, with a wide range reported across studies. Additionally, the definition of "asymptomatic" may vary across studies, depending on which specific symptoms were assessed.

Patients with asymptomatic infection may have objective clinical abnormalities. As an example, in a study of 24 patients with asymptomatic infection who all underwent chest computed tomography (CT), 50 percent had typical ground-glass opacities or patchy shadowing, and another 20 percent had atypical imaging abnormalities [2]. Five patients developed low-grade fever, with or without other typical symptoms, a few days after diagnosis. In another study of 55 patients with asymptomatic infection identified through contact tracing, 67 percent had CT evidence of pneumonia on admission; only two patients developed hypoxia, and all recovered [3].

As above, some individuals who are asymptomatic at the time of diagnosis go on to develop symptoms (ie, they were actually presymptomatic). In one study,

symptom onset occurred a median of four days (range of three to seven) after the initial positive RT-PCR test [4].
