From asymptomatic to critical illness: decoding various clinical stages of COVID-19

The clinical course of COVID-19 is variable, with clinical manifestation ranging from 81% mild course to 14% severe course along with 5% critical course in patients. The asymptomatic course is reported to potentially range between 20% and 70% (avg. 33%). A more severe course is seen in the elderly, those with various chronic diseases, and the immunosuppressed, where the case fatality rate is higher in these risk groups. The disease progresses with various symptoms, such as fever, cough, shortness of breath, malaise, myalgia, taste and smell disorders, diarrhea, sore throat, headache, and conjunctivitis. The disease begins with shortness of breath, indicative of lung damage, after an average of 7 to 10 days, and progresses in ARDS, sepsis, and septic shock. Some patients quickly enter shortness of breath, while others gradually develop shortness of breath and chest tightness and burning. The risk factors for a poor prognosis are age, comorbidities, and changes in laboratory tests. Secondary bacterial and fungal infections frequently develop with steroids and immunosuppressants, especially in the intensive care unit. Frequent complications in hospitalized patients include pneumonia (75%), ARDS (15%), acute renal failure (9%), and acute liver injury (19%). An increased incidence of heart damage is observed, including acute heart failure, arrhythmias, and myocarditis. Of the patients hospitalized due to COVID-19, 10%­25% present with prothrombotic coagulopathy, resulting in venous and arterial thromboembolic events. The most common extrapulmonary symptom is neuropsychiatric involvement, frequently accompanied by insomnia, an impediment to remembering, and an altered state of consciousness. During the course of COVID-19, patients undergo some pathological changes (severe lymphopenia, high levels of C-reactive protein, D-dimer, ferritin, etc.) depending on the condition and exposure level of the affected systems as shown by various laboratory tests. The relevant tests are the guiding elements of risk assessment, clinical monitoring, disease severity, and prognosis setting and therapy decision-making processes.

COVID-19: pathogenesis, genetic polymorphism, clinical features and laboratory findings

COVID-19 caused by a novel agent SARS-CoV-2 progressed to a pandemic condition and resulted in a major public health concern worldwide, leading to social and economic issues at the same time. The pathogenesis of COVID-19 starts with the bonding of the virus to ACE2 receptors expressed in many tissues, and the triggered excessive immune response plays a critical role in the course of the disease. The cytokine storm that occurs upon excessive production of pro-inflammatory cytokines is considered responsible for the severe progression of the disease and the organ damage. However, the accurate pathophysiological mechanism of the disease, which progresses with various clinical presentations, is still substantially unknown. While various studies have been conducted on the effect of genetic polymorphism on the course and severity of the disease, the presence of a significant effect has not been proven yet. The clinical course of the disease is variable, with clinical representation ranging from 81% mild course to 14% severe course along with 5% critical course in patients. Asymptomatic course is considered to be higher than expected, although its frequency is not known exactly. Older adults and those with comorbidities are exposed to a more severe disease course. The disease progress with various symptoms, such as fever, cough, dyspnea, malaise, myalgia, taste and smell dysfunctions, diarrhea, and headache. A range of complications (acute respiratory distress syndrome, thromboembolic conditions, arrhythmia and cardiac events, secondary infections) could be seen during the course of the disease. Varied laboratory tests are vital to determine these verity and prognosis of the disease, along with the condition and exposure of the affected systems during thecourse of COVID-19.