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COVID-19 (Coronavirus Disease 2019) is a respiratory infection caused by SARS-CoV-2, a virus related to the cause of SARS. This variant arose in 2019 in China near the city of Wuhan and quickly spread globally to cause the most significant pandemic since AIDS. Rapid sequencing of its genome and development of rapid diagnostic testing and a COVID vaccine within one year of the start of the outbreak have slowed the spread and reduced mortality, but frequent mutations give rise to novel strains of COVID which necessitate continued vigilance and updated booster shots.

COVID-19 variants that have been identified in the past 3 years include alpha, beta, gamma, delta and omicron variants. Omicron variants include BA.1, BA.2, BA.3, BA.4 and BA.5 as well as recombinant (XE) strains.


         Cause: SARS coronavirus 2

         Microscopy: enveloped ssRNA virus with club-shaped glycoprotein spikes

         Symptoms: fever, cough, shortness of breath, loss of taste/smell, aches

         Transmission: Respiratory (droplets), close contact

         Complications: Pneumonia, cardiac damage, tissue death, long-term lung damage; Mortality rate ~1% of positive tests

         Pathogenesis: respiratory epithelium infection via ACE-2 receptor, viremia, cytolytic replication in other tissues bearing ACE-2 (blood vessels, kidneys, GI)

         Treatment: remdesivir, convalescent plasma


1.    https://www.cdc.gov/coronavirus/2019-nCoV/index.html

2.    https://www.bmj.com/content/371/bmj.m3862

3. https://www.nature.com/articles/s41579-022-00713-0