25 virology terms to help you understand outbreaks, from the common cold to COVID-19
The world is just beginning to come to terms with the pandemic caused by COVID-19. As various parts of the country and world employ pandemic interventions such as shelter-at-home recommendations, a better understanding of the basic biology behind outbreaks, viruses, and how they work can help to clarify why these steps are so crucial from a scientific standpoint.
Stacker consulted encyclopedias and public health websites to compile a list of 25 virology terms. These terms help build background knowledge on what viruses are, how contagious they are, how they work in living cells, how they spread, and how they affect humans. These definitions illustrate the difference between the common cold and the COVID-19 virus and why COVID-19 is so deadly. The terms also help show why self-isolation and quarantine—as well as social distancing—are critical now, as these will help “flatten the curve” to prevent an exponential rise in COVID-19 cases and deaths. The gallery will also highlight terms such as capsid, R0, and zoonosis that are increasingly used in news stories.
What becomes clear with the basic science of COVID-19 is that the best and most effective way to love and care for others right now is to respect recommendations for social distancing. This is the most immediate, strongest action any of us can take to stop the spread.
Keep reading for fast lessons in droplet spread, community transmission, quarantine, and many more COVID-19-related terms.
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A virus is a microscopic, infectious cellular invader. Viruses insert themselves into living cells where they replicate. They can infect most life forms: from bacteria to plants to animals. Every cellular organism studied so far has its own viruses. Millions of viruses are found across all ecosystems and life forms on Earth, with about 5,000 of these described by science.
A bacteriophage—or phage for short—is a virus that specializes in infecting bacteria. Most viruses are bacteriophages. These particular types of viruses are made of proteins that infect the bacterial cell, then they enclose the DNA or RNA genome within the cell. Bacteriophages are the most common entities on Earth and are found everywhere bacteria exist, which is across all environments on Earth.
Viruses specialize on all different forms of cellular life; each virus evolved to infect different forms. Animal viruses infect only animals, and two fields of study separate their study. For non-human animals, the field is known as “veterinary virology,” while “medical virology” is the study of viruses and human beings. Viruses that affect humans are the most studied with many areas of research.
The protein shell of a virus that helps it enter its target cell is called a capsid. It protects the gene material of the virus. Structures of capsids vary widely and may consist of numerous proteins.
Some capsids build what are called “viral envelopes” from the cell itself. These are lipid membranes the virus builds around itself, with lipid material of the cell’s inner membrane. Viral envelopes are thought to help the virus infect the target cell. Lipids are the cell’s fatty acids and are not water soluble.
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Endocytosis is the term for when a virus enters its target cell. Viruses infect their cells in various ways. In some cases, the virus enters the cell but leaves the capsid behind, on the outside of the cell. In enveloped viruses, the viral envelope fuses directly with the cell membrane then it enters the cell. Inside the cell, the capsid degrades and the genetic material of the virus is released.
Some viruses have a special trait that allows them to enter and infect a cell, then go dormant. The virus may replicate in the cell at first, then stop. Viral latency refers to the time that viral genetic material can remain in the cell before being reactivated. If reactivated, the virus can reinfect the host without the host being re-exposed. HIV is known to have viral latency.
Zoonosis is when an infectious disease is transmitted from other vertebrate animals to humans. These kinds of infections can occur in natural conditions because vertebrate animals are genetically similar to humans. Some examples include the black plague, transmitted by rats; rabies, transmitted by bats, raccoons, and dogs; and anthrax, transmitted by sheep. More recently emergent human diseases like HIV, Ebola, and SARS likely arose from zoonosis.
Droplet spread refers to transmission when coughs, sneezes, and breath travel some distance from an infected person to a non-infected person. Generally people have thought that close proximity is necessary for droplet spread, but new research reported by the Journal of the American Medical Association (and motivated by the coronavirus pandemic), shows that infectious droplets can travel as far as 23 to 27 feet.
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