CHAPTER 4: Clinical Presentation, Pathophysiology and Histopathology
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Published:27 Apr 2022
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Special Collection: 2022 ebook collection
C. Hughes, I. Mahalaxmi, N. Senthil Kumar, S. S. Sudalaimuthu Raja, R. Thangarasu, S. Warren, and M. Waters, in The Coronavirus Pandemic and the Future Volume 1, ed. M. D. Waters, A. Dhawan, T. Marrs, D. Anderson, S. Warren, C. L. Hughes, ... C. L. Hughes, The Royal Society of Chemistry, 2022, pp. 63-98.
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This chapter describes the various modes of viral transmission, the signs and symptoms, and the distinct clinical trajectory and disease spectrum of coronavirus disease 2019 (COVID-19). It also describes the mechanism of severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) invasion into host cells and the various disease manifestations of COVID-19. Direct transmission of the virus is from person to person through respiratory droplets or aerosols and physical contact, while indirect transmission is through contaminated surfaces. It is not clear why a substantial proportion of SARS-CoV-2-infected individuals report few, if any, symptoms and recover completely, while chest computed tomography (CT) provides evidence that viral pneumonitis is present in >90% of symptomatic cases within 3–5 days of onset. Commonly observed symptoms of COVID-19 are tiredness, headache, fever and dry cough. Patients also present with non-respiratory symptoms that include gastrointestinal disorders, olfactory dysfunction (impairment or loss of smell), loss of taste, neurological problems and cardiovascular effects. In patients with pre-existing conditions such as immune compromise, hypertension and cardiovascular disease, obesity and diabetes, symptoms may quickly progress to multi-organ conditions including multi-organ failure, sepsis, and septic shock. Overall, clinical features have been described based on the increasing severity of the symptoms as asymptomatic/pre-symptomatic, mild, moderate, severe and critical. The progression from mild to moderate symptoms usually occurs between 7 and 14 days, consistent with the recommended quarantine period following suspected exposure to the virus. Finally, the various morbidities resulting from the disease are discussed in detail.