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Overview of COVID-19

About the Disease

SARS-CoV-2 is the novel coronavirus that causes COVID-19.  SARS-CoV-2 is a one in a family of seven coronaviruses. Coronaviruses describe a +sense single stranded RNA virus with about 27K base pairs.  There are 7 total corona viruses that cause human infection including SARS, MERS, SARS CoV 2, 229E, NL63, OCH3 and HKU11.  There are alpha and beta coronaviruses but SARS CoV 2 falls into the beta category.  Human coronavirus NL63, SARS CoV 1 and SARS CoV 2 both bind to the ACE2 receptor located on the vascular endothelium, type 2 pneumocytes and small intestine epithelial cells.2  This would obviously lead to symptoms of cough, shortness of breath, perhaps chest pain and loose stool.  All of these symptoms have been reported. Patients usually present with dry cough, fever, possible congestion and shortness of breath.  They may also present with loose stool.3 

It has been suggested we should stage COVID-19.  The first stage would be early infection followed by stage 2, pulmonary involvement without hypoxia (2A) or with hypoxia (2B).  The final stage would be systemic hyperinflammation.4.  Once the virus attaches itself to the type 2 pneumocyte, this leads to cellular recruitment to the area to help fight infection.  This communication is done through cytokines. This will lead to a viral pneumonia and potentially hypoxia and if this continues, a cytokine storm can ensue.  This would include ARDS and possibly systemic shock. 2 major cytokines have been identified and may lead to the predominant inflammatory syndrome that leads to disease severity, IL-6 and GM-CSF.5,6

Understanding the immunology and pathophysiology of COVID-19 has led to potential therapies. Several trials are being conducted by WHO which are ongoing.  Most medicines involved include Kaletra (lopinavir/ritonavir), Remdesivir, Hydroxychloroquine, azithromycin, Tocilizumab, and Sarilumab (both IL-6 inhibitors).7  This disease has affected hundreds of thousands of people and has led to thousands of deaths worldwide.  We all continue to be vigilant fighting this disease and understand that as we battle this condition along with our healthcare team, personal protective equipment seems to be of the utmost importance.  

1.  Microbiology 2nd edition Harvey et al 

2.  Chen, N et al Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study LANCET 2020

3. Gu J, Han B, Wang J, COVID-19: Gastrointestinal manifestations and potential fecal-oral transmission, Gastroenterology (2020) 

4. Siddiqu HK, Mehra MR. COVID-19 Illness in Native and Immunosuppressed States: A Clinical- Therapeutic Staging Proposal. Journal of Heart and Lung Transplantation.

5. Hong-Yi Zheng1, et al Elevated exhaustion levels and reduced functional diversity of T cells in peripheral blood may predict severe progression in COVID-19 patients Cellular&MolecularImmunology

6. Zhou, Y et al Pathogenic T cells and inflammatory monocytes incite inflammatory storm in severe COVID-19 patients 

7. AdaptiveCOVID-19TreatmentTrial. ClinicalTrials.gov identifier: NCT04280705. 

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