Part I : COVID-19 stands for coronavirus disease 2019. The virus that causes COVID-19 is medically called (SARS-CoV-2) which is short for severe acute respiratory syndrome coronavirus 2. It is in the same family as the severe acute respiratory syndrome (SARS) virus and Middle East respiratory syndrome (MERS) virus.
The SARS-CoV-2 can evolve over time which can be called mutations. The mutations can develop into different variants including: alpha, beta, delta, epsilon, gamma, and mu. The variants can increase the transmission rates of different strains and be associated with greater disease severity.
Alpha (B.1.1.7 lineage) was first identified in the United Kingdom in late 2020. Beta (B.1.351 lineage) was identified in South Africa in late 2020. Delta (B.1.627.2 lineage) was first identified in India in December 2020. Epsilon (B.1.427 and B.1.429 lineages) was first identified in Southern California in January 2021. Gamma (P.1 lineage) was found in Japan in travelers from Brazil in December 2020.
Globally, over 200 million confirmed cases of COVID-19 have been reported and cases have been reported in all continents. Person-to-person spread is the main mode of transmission. The period of greatest infectiousness is in the earlier stages of illness. The risk of transmission increases with the close contact and amount of time of contact. But, the risk of transmission from a person who has no symptoms appears less than from one who has COVID-19 symptoms. Other modes of transmission can include environmental contamination or animal contact but these are less well documented.