25th January 2021 | Knowledge Base
Bacteria are single-celled microorganisms and some of the earliest forms of life. Believe it or not, you can find bacteria everywhere, in the air, in the soil, in the water, in our bodies and the bodies of animals and plants. Some species can live under extreme conditions of temperature and pressure. Most bacteria – including those found in our body, are harmless and sometimes even helpful. However there are certain types of bacteria that can cause infections. Some infections caused by bacteria include, cholera, syphilis and leprosy.
Bacteria are single celled, but these cells are all prokaryotic. This means they do not have a nucleus or any other structures which are surrounded by membranes. So the chromosomal DNA of bacteria cells are found loose in the cytoplasm. See our class on the human cell for a comparison in structure.
Viruses are smaller than bacteria and can’t survive or replicate without a living organism to attach itself to. Also, unlike bacteria, most viruses do in fact cause disease within the host they have inhabited. Some common virus caused diseases include the common cold, AIDS, herpes and chickenpox.
It should be known, viruses can infect all types of life forms, from plants to animals and even micro organisms, including bacteria. Viruses, before they are inside an infected cell, or are in the process of infecting a cell, exist in the form of independent particles. These particles are too small to be seen, even with an optical microscope.
Once infected, the infections can spread in many ways. For example in plant life, viruses could be passed from plant to plant by insects, landing and feeding on the plant sap before moving onto another plant. In animals and humans there are various ways viruses can spread, depending on the virus. Some are spread by blood sucking insects, some by sneezing or coughing, and others through sexual contact. It should also be noted, that viruses have what is called a host range; this host range can be narrow, meaning it is only capable of infecting a few species, or broad, meaning it can infect many.
Since many viruses can infect a large number of different cell types, genetically modified viruses often are used to carry foreign DNA into a cell. There is a good example of this in the movie The Bourne Legacy. In the movie, live virus stems were inserted into the bodies of the agents in order to modify their DNA, making them both stronger and smarter. In the real world, such techniques are used to administer what is known as gene therapy; still considered experimental, it is a technique that uses genes to treat or prevent disease.
Viral and bacterial infections in humans and animals often provoke an immune response which usually successfully eliminates the virus/bacteria. However this is not always the case, depending on the infection, and also the strength of the immune system. Check out our short write up on The Immune System for further information.
Pandemics
Whenever a new virus or bacterium appears, depending on how much it spreads, it can cause what is known as a pandemic. Now in 2020/21, we are actually witnessing one in front of our very eyes. Covid-19, A Corona virus disease, has been making its way through the world, infecting millions. But how bad is this pandemic in comparison to others? And how soon can we expect it to end?
A pandemic is defined as a disease which is prevalent over a whole country, or the whole world. As we are living today, we can see the effect of the latest pandemic. It has been said to have infected several million people, and caused nearly 2 million deaths worldwide. Because it is a new virus, treatments, immunity and ways to fight the virus can be relatively difficult to identify. Exactly how the virus works, and the type of DNA it targets can also be a challenge to determine. A question being asked right now, is why death rate in the continent of Africa has been so low when compared with certain other places. The answers to these questions remain unknown to the masses, but as time goes on, these things will likely become clearer.
Some previous pandemics may give us an idea as to how exactly this latest virus situation may develop. Below are some examples of outbreaks throughout recent history.
FLU PANDEMIC (1918)
Death Toll: 20 -50 million
Cause: Influenza
Recorded as taking place between the years 1918 and 1920, a deadly outbreak of influenza tore across the globe and infected over a third of the world’s population. It ended the lives of between 20 and 50 million people, but the amount infected was closer to 500 million. This was a particularly worrying pandemic as the disease was striking down healthy young adults, whilst leaving those with apparently weaker immune systems alive.
THE PLAGUE (1346-1353)
Death Toll: 75 – 200 million
Cause: Bubonic Plague
From 1346 to 1353 an outbreak of the Bubonic plague terrorized the planet killing somewhere between 75 and 200 million people. It was said that the plague most likely spread by way of fleas that were living on rats that were on board ships. The results were devastating.
MERS (2012 – Present)
The respiratory illness is caused by the coronavirus MERS-CoV. It was first reported in Saudi Arabia and has killed more than 850 people since then. It likely originated in bats and jumped to dromedary camels, the source of human infections. Unlike the Covid-19 virus, it does not transmit easily from person to person.So as we can see from some of the examples above, there are two main things to concern yourself with when dealing with a disease. How effective it is at spreading amongst humans, and how deadly it is to humans. Some viruses are hugely contagious, but not necessarily that deadly. Others are the opposite. When the two combine, is when you may just have a serious problem.
Keep in mind that it can sometimes be difficult to know exactly how much a disease is spreading, especially when that virus is effecting different people in different ways. Some may have the virus, and simply never know they had it, because symptoms did not manifest in the same way as we’ve seen with others. It therefore remains possible that the virus itself, is making changes to the genetic system that we may not know about for years to come.
Additional Information
There are some Viruses that can mutate rapidly and therefore spawn new types. This can make it difficult for the immune system to effectively defend against the invader, and therefore the host may have little protection. The common cold is an example of this fact, and is why most humans remain vulnerable to a cold throughout their life. The virus is constantly changing, and therefore avoiding immediate elimination when it enters the body. The immune system will remember its predecessor but will not have the tools to immediately get rid of this new version.
