What is a virus - Blog - Urban Plate Health - Nutrition and Lifestyle based in London and Essex - Urban Plate Health - Nutrition and Lifestyle based in London and Essex

What is a virus?

10/5/2020

The current world that most of us live in is an unprecedented situation. Most of the world has gone into lockdown to avoid contracting COVID19. This has had drastic effects on most aspects of life. What we used to take for granted currently does not seem the norm. A simple trip to go watch a movie, pop to the gym or to meet friends for a coffee has been replaced with stay at home isolation and only necessary trips to control the spread of COVID19. Whether you agree with the current lockdown procedures or not is not the subject of this blog post however. In this post I'm going to focus on educating you on what a virus is and how they work.

A virus is a living thing. It's not an object or something that can be taken for granted. For starters, viruses are easily the most abundant life form on Earth, if you accept the proposition that they're alive. Try multiplying a billion by a billion, then multiply that by ten trillion, and that (10 to the 31st power) is the mind-numbing estimate of how many individual viral particles are estimated to populate this planet [1]. Because of the great diversity among viruses, biologists have struggled with how to classify these entities and how to relate them to the conventional tree of life. They may represent genetic elements that gained the ability to move between cells. They may represent previously free-living organisms that became parasites. They may be the precursors of life as we know it [2].

So, now we have some background information on the amount of viruses out there, let's go into how they can enter the human body and the mechanisms they use to replicate/grow and mutate.

Viruses during transmission to the human body contain either DNA or RNA as its genetic material and are surrounded by a protein shell called a capsid and sometimes known as an envelope. Once the virus has passed into the host cell, the viral package is unpacked which results in the hijacking of that cell. The interaction between the host and the virus now depends on the viral genome.

In terms of viruses that use the DNA mechanism, viral DNA is transported to the nucleus of the hijacked cell for transcription and translation, but it remains as a separate module from the host DNA. Examples of these viruses are the herpes viruses, pox viruses and human papilloma viruses. DNA has a large genome with slow replication and DNA repair mechanisms.

For RNA viruses, the viral genome can remain in the host cell's cytoplasm and is translated into proteins or as a messenger RNA. What does this mean? RNA viruses are required to replicate their own genome as the host cell is unable to replicate the RNA genome template. Some examples of RNA viruses are the Rhinovirus (common cold), Hepatitis A and Hepatitis C viruses. RNA has a small genome, meaning it is very dependent on the host, it produces rapid replication and has no RNA repair mechanisms.

Now I could go into genome sequencing, talk about single stranded and double stranded DNA mapping, protein synthesis etc, but I would lose most of you, so i’ll keep it simple and say re-read the above two paragraphs again.

Once inside a cell, viruses release their genomes and also disrupt or hijack various parts of the cellular machinery. Viral genomes direct host cells to ultimately produce viral proteins (many a time halting the synthesis of any RNA and proteins that the host cell can use). Ultimately, viruses stack the deck in their favor, both inside the host cell and within the host itself by creating conditions that allow for them to spread. For example, when suffering from the common cold, one sneeze emits 20,000 droplets containing rhinovirus or coronavirus particles, according to "Molecular Biology of the Cell." Touching or breathing those droplets in, is all it takes for a cold to spread [3].

Unlike human cells or bacteria, viruses don't contain the chemical machinery (enzymes) needed to carry out the chemical reactions for life. Instead, viruses carry only one or two enzymes that decode their genetic instructions. So, a virus must have a host cell (bacteria, plant or animal) in which to live and make more viruses. Outside of a host cell, viruses cannot function. For this reason, viruses tread the fine line that separates living things from nonliving things. Most scientists agree that viruses are alive because of what happens when they infect a host cell [4].

Viruses lie around our environment all of the time just waiting for a host cell to come along. They can enter us through the eyes, nose, mouth or breaks in the skin. Once inside, they find a host cell to infect. For example, cold and flu viruses will attack cells that line the respiratory or digestive tracts. The human immunodeficiency virus (HIV), which causes AIDS, attacks the T-cells of the immune system. Regardless of the type of host cell, viruses follow the same basic steps to replicate [4]:

A virus particle attaches to a host cell.
The particle releases its genetic instructions into the host cell.
The injected genetic material recruits the host cell's enzymes.
The enzymes make parts for more new virus particles.
The new particles assemble the parts into new viruses.
The new particles break free from the host cell.

In terms of how you feel when infected by a virus, this depends on the type of virus you have been infected with. A common Rhinovirus will for most people result in symptoms common with a cold. This results in coughing, sneezing, body aches as well as higher temperature sometimes as common symptoms. Note that higher temperature is your body heating itself to ‘burn’ the virus out of its system. In terms of recovery from the common cold, roughly 7-10 days of rest, intake of warm fluids and an increase in hearty soups as well as a higher intake of vitamin C can help facilitate this.

Other viruses, such as the Herpes viruses or Hepatitis viruses demonstrate different symptoms in the body, and for the above two viruses mentioned, you will require a consultation with a medical profession and require medicine to help with the symptoms of these viruses.

An example would be the Herpes Simplex type 1 or 2 viruses. They commonly cause cold sores and can be caught on most parts of the body, however lips and genital parts seem to be the most common area. Antiviral tablets may be prescribed for cold sores. If you get an unacceptable number of outbreaks, talk to your doctor. Antiviral tablets are a more effective way of treating and preventing cold sores than antiviral creams [5]. Other factors such as diet, lifestyle and how much sun exposure can contribute to the recurrence of cold sores (discussing this will be a blog in itself).
Examples of the most famous viruses in the past have been [6,7]:

Marberg virus
Ebola virus
Rabies virus
HIV
Smallpox
Dengue virus
H5N1 bird flu
SARS-CoV
MERS-CoV
H1N1
H7N9 bird flu
2019-nCoV

Now you should have a good grasp of what viruses are and how they work inside the human body. In my next blog, I will discuss COVID19 in detail, what it is, how it attaches itself to a cell, how the body reacts to it and what can be done to avoid, or as I like to think, to live alongside COVID19.

References