You wake up in the morning and you are not yourself as your body isn't how it used to be. You are certain that foreign invaders now have control o your body, and do not know to treat yourself because you do not know foreign invader is disturbing you. To properly treat yourself, you need to know which of the invader is causing the discomfort you are feeling.
We are commonly attacked by Viruses or Bacteria, except for underdeveloped countries were malaria parasite is quite common than bacterial infection. It is important to not start treating viral infections with antibiotics because antibiotics would not do the work, and identifying if the cause of the disease is a virus or bacteria can save life.
Image From Research gate
Both viruses and bacteria are microscopic which means they cannot be seen by the naked eyes but while they are both very small, viruses are extremely smaller than bacteria as even the biggest virus is still extremely smaller than the smallest bacteria. Both organisms can get into the human body through openings commonly the mouth and nose since they are the most active big openings in our body.
Although I just made mention of the both organism being small, I need to make it clear that while they are both microscopic, one is living and the other is a nucleic acid. Bacteria is alive since it is made up of cells, it can grow and reproduce new ones, it responds to environmental stimuli, can pass genetic information, and can maintain internal balance but for virus, they do not meet the criteria for a living thing.
Image from NDLA
Bacteria is common in our environment and our body as there are trillions of bacteria cells in our body as they outnumber the cells in our body at a ratio of 10:1 for Bacteria to Human cells but then, not all the bacteria in our body are healthy as a lot of them make up our normal micro floral. If these micro floral aren't in the body, the body can become an easy access for infections as well as certain activities would not be carried by the body.
Remember that I didn't mention that viruses are noon-living because the answer is complicated. Depending on who you ask in the scientific community, so people can say they are non-living, while some might say they are, so we can just say that they are in the gray area between living and non-living. They will only reproduce after they have hijacked the host immune systems. They change the genetic information of cells so as to suit their needs.
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Bacteria uses evolution by natural selection, and that is how they get some characteristics from other bacteria cells. Also, why viruses are not living in essence, they evolve over time and this is done through mutation which is as a result of random mistakes in DNA.
One difference that is beneficial to humans when it comes to viruses that isn't found in bacteria is that when a person is infected by a particular strain of virus, and overcomes it, then the person is immune to the virus as the body develops resistance to it. Another importance of viruses to humans is Bacteriophages.
These set of viruses help to fight against bacteria since they target certain types of bacteria and destroy them. As at the time when I was researching for this post, I didn't see any bacteria that attacks and destroy viruses, but we could see them in the future as science keeps investigating the numerous types of bacteria available but then there are a list of viruses that attacks and kill bacteria.
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Before you completely shut out viruses thinking they are not in your system, et me inform you that as a result of viruses leaving a part of their DNAs in us for centuries, we now have 10 percent of our human DNA being viral DNA. That is that on that!! C'mon, that sounds weird but I like how I said it.
When you are not feeling too well, the first thing to know is what type of microorganism or particle can be causing the sickness. It will be wrong to treat a viral disease with antibiotics and it has no effect on viruses. For viruses, using antiviral medication is the first way to treat a virus. The antiviral drug is only functional when in the system of the person who took it, but then another type of treatment is vaccine and it can be used to kill both viruses and bacteria.
Reference
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3160642/
https://newsinhealth.nih.gov/2012/11/your-microbes-you
https://www.sciencedaily.com/releases/2016/11/161128151050.htm
https://www.nih.gov/news-events/news-releases/nih-human-microbiome-project-defines-normal-bacterial-makeup-body
https://www.scientificamerican.com/article/are-viruses-alive-2004/https://www.scientificamerican.com/article/are-viruses-alive-2004/