The severe acute respiratory syndrome coronavirus 2 ( SARS-CoV-2 ), initially provisionally called "2019-nCoV", sometimes "Wuhan's coronavirus", or "COVID-19 virus", was first identified in humans in the Chinese city of Wuhan, Hebei province, and cases have been confirmed in other countries.
Coronaviruses belong to the Coronaviridae family in the order Nidovirales Corona and have crown-like tips on their outer surface, which is why they were called coronaviruses. These can cause infections in people and have a positive-sense RNA genetic material, that is, they directly serve for protein synthesis, causing a higher speed in the generation of new virus copies in the infected cell.
These are surrounded by a layer of fat and proteins, and their size is approximately one hundred nanometers. In addition to the presence of several structural proteins on its surface such as E (envelope), M (membrane) and N (nucleocapsid), there is Spike Protein, or S Protein , which is a glycoprotein spike that binds strongly to the enzyme ECA2, present in our cells, which makes their infection easier.
Upon entering the human cell, it replicates in the nucleus and produces viral particles that leave the cells where they were produced, migrating to the rest.
Figure 1- Covid-19 structural proteins
Mutations often occur during replication that lead to new variants of the virus, but these often do not change the way the virus behaves and may even make it less infectious than the original virus. Rarely, these mutations can also alter you in important ways, making you more infectious or even more resistant to the immune system. The variants in the United Kingdom , India , Brazil and South Africa are examples of the latter case in which the virus undergoes mutations that make it more infectious and dangerous to health.
Based on current evidence, the virus is transmitted through two means:
- Direct contact : when a spread of respiratory droplets occurs when, for example, an infected person coughs, sneezes or speaks and these can be inhaled by nearby people;
- Indirect contact : when contamination occurs through hand contact with a contaminated surface or object.
Figure 2- Covid-19 transmission media
Among the most common symptoms of Covid-19, it is possible to highlight fever, dry cough and tiredness, and symptoms such as muscle pain, headache, loss of smell or taste and diarrhea are also frequent. In more severe cases it can lead to severe pneumonia with acute respiratory failure, kidney and other organ failure and even death.
Figure 3- Covid-19 symptoms