COVID19 Fact Sheet #1: The Virus
These fact sheets will provide data about characteristics, diagnosis, management, and prevention of COVID19. Fact sheet #1 will discuss known facts about the virus itself, as an in depth understanding of it is essential to develop cures and vaccines, and many people – disoriented by sensationalist media reports – keep asking themselves, how modern medicine would not able to identify a threatening pathogen in the months since its occurrence.
At the end of 2019, a novel coronavirus was identified as the cause of pneumonia in Wuhan, a city in the Hubei Province of China. It rapidly spread, resulting in an epidemic throughout China, followed by an increasing number of cases in other countries throughout the world. In February 2020, the World Health Organization designated the disease COVID-19, which stands for coronavirus disease 2019. The virus that causes COVID19 is designated “severe acute respiratory syndrome coronavirus 2” (SARS-CoV-2), as there has been a previous SARS pandemic in 2003 (Previously, the novel virus was referred to as 2019-nCoV.)
COVID19: Viruses – general information
A virus is a small particle, that cannot reproduce by itself. Once it infects a susceptible cell, however, a virus can direct the cell to produce more viruses of its kind. The entire infectious virus particle consists of the genetic information, and an outer shell of protein. The simplest viruses contain only enough information to encode four proteins. The most complex can encode 100 to 200 different proteins.
Viruses that affect plants have been discovered as early as 1935. There are viruses affecting animals, humans and even bacteria. In many cases, viruses utilize cellular enzymes for multiplying their own genomes, and all are using normal cellular protein “factories” for synthesis of their proteins.
A virus that infects only bacteria is called a bacteriophage. Viruses that infect animal or plant cells are referred to generally as animal viruses or plant viruses. Most animal viruses do not cross to humans, yet some do.
All retroviruses and some other animal viruses can even integrate their genomes into host-cell chromosomes. This may lead to abnormal cell function, or even cancer. Aside from causing many diseases, viruses are important tools in cell biology research.
Understanding of COVID19 is evolving. Coronaviruses are use RNA to code their genetic information, and appear with a crown-like appearance under an electron microscope (corona is the Latin term for crown) due to the presence of spike like molecules on the virus shell.
Members of this large family of viruses can affect lungs, bowel, liver or nervous in different animal species, including camels, cattle, cats, and bats. To date, seven human coronaviruses are known to be capable of infecting humans. Some of them were identified in the mid-1960s, while others were only detected recently. In general, estimates suggest that 2% of the world population are carrying human Coronaviruses while being healthy, and that these viruses are responsible for about 5% to 10% of cases of common cold.
Full-genome sequencing and analysis of its origins indicate that the novel coronavirus, that causes COVID-19, belongs to the same family, as the severe acute respiratory syndrome (SARS) virus of 2002, using the same receptor, the angiotensin-converting enzyme 2 (ACE2), to enter cells.
The Middle East respiratory syndrome (MERS) virus, another coronavirus, appears more distantly related. Probably the novel coronavirus originated in bats; whether COVID19 virus is transmitted directly from bats or through some other mechanism (eg, through an intermediate host) being as of now unknown. In China, two different types of SARS-CoV-2 were identified, called type L (accounting for 70 percent of the strains) and type S (accounting for 30 percent). The clinical implications of these findings are uncertain.
Lodish H, Berk A, Zipursky SL, et al.: Molecular Cell Biology. 4th edition. New York: W. H. Freeman; 2000.(https://www.ncbi.nlm.nih.gov/books/NBK21523/)
Marco Cascella; Michael Rajnik; Arturo Cuomo; Scott C. Dulebohn; Raffaela Di Napoli: Features, Evaluation and Treatment Coronavirus (COVID-19). (https://www.ncbi.nlm.nih.gov/books/NBK554776/ )