Fundamental Basis of COVID-19 Pathogenesis

The Study of the Outbreak of Coronavirus Infection in a General Hospital in Almaty

The study aimed to identify the possible causes of COVID-19 outbreak and its development in a general hospital in Almaty (from April 11 to May 6, 2020), where 682 persons were identified with a COVID-19. 546 were hospital employees (48.9%), including doctors (57.8%), nurses (53.4%), junior medical personnel (54.4%) and other personnel (23.3%), and also among 136 patients. The attack rate among women was 50.0%, and incidence rate was higher amongst young employees < 30 years old (57.0%). The analysis showed that there was a failure of the management of the medical personnel in such critical situation.

Respiratory epithelium: Place of entry and / or defense against SARS-CoV-2 virus

Coronavirus Disease (COVID-19) is caused by the RNA virus SARS-CoV-2. The primary receptor for the virus is most likely Angiotensin-converting enzyme 2 (ACE2), and the virus enters the body by infecting epithelial cells of the respiratory tract. Through the activation of Toll Like Receptors (TLRs), epithelial cells begin to synthesize various biologically active molecules. The pathophysiology of the COVID 19 is primarily attributed to the hyperactivation of host's immune system due to direct damage to the cells, with consequent release of proinflammatory substances, but also due to the activation of the innate immune response through the activation of alveolar macrophages and dendrite cells (DC). A strong proinflammatory reaction causes damage to alveolar epithelial cells and vascular endothelium. Respiratory epithelial cells, alveolar macrophages and DC are likely to be the most important cells involved in the innate immune response to the virus, since prolonged and excessive SARS-CoV-2-induced activation of these cells leads to the secretion of cytokines and chemokines that massively attract leukocytes and monocytes to the lungs and cause lung damage.