What would you think of when someone mentions the word virus? Probably COVID-19, the virus that has taken thousands of lives and put us in a global pandemic. But what are viruses actually? How can they be invisible to the naked eye but affect so many people's lives? In this article, you are going to learn about viruses and how they function.
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For many years, scientists argued over whether viruses are living or nonliving entities. They ultimately came to the conclusion that viruses are non-living because they lack important characteristics of living organisms such as growth, development, metabolism, and respiration. Additionally, they can only reproduce with a host or with the help of other living cells.
Viruses are made up of nucleic acid and a protein capsid, and lack a nucleus, organelles, cytoplasm and cell membrane. However, some larger viruses also have an envelope, or an additional layer surrounding the capsid, to protect themselves. Viruses have either DNA or RNA, but they don’t contain both like human beings do.
Another characteristic of viruses worth noticing is that they are very specific and only attack certain cells. For example, rabies only attacks brain or neuron cells, HIV only destroys Helper T cells, etc. A virus recognizes certain cells and infects them by matching its surface marker with a receptor site on a cell.
Now that we know the basic characteristics of viruses, we can move on to how they reproduce.
There are two cycles of viral reproduction known as the lytic cycle and the lysogenic cycle.
Lytic cycle:
Viral genes direct the host cell to make new viruses.
Host cell uses its own energy to make copies of viruses.
The cell bursts, killing the host cell, and the virus is released to infect other cells.
Lysogenic cycle:
A provirus is formed and may not affect the functioning of the cell.
The provirus is copied every time the cell reproduces.
At any time the provirus can be activated and can enter the lytic cycle.
Learning about the replication of viruses leads us to the next question: How do viruses spread between people?
There are three ways in which infectious disease spreads:
Through the air: When a person that is infected sneezes or coughs, the droplets containing small infectious particles get released into the air. If another person breathes in the particles, he/she may get infected.
Through direct contact: Touching an infected person or animal directly, or their body fluid (blood, urine, saliva, etc.) increases the risk of getting infected. This is also why washing hands frequently is extremely important.
Through contact with contaminated surfaces or objects: If you touch a surface or object that has been contaminated by an infected person or animal, you are at risk for getting infected.
We are exposed to pathogens every day, but because of our immune system, we don’t get infected easily. However, there are some other ways in which we can avoid infections:
Vaccination: Injecting a vaccination stimulates the immune system to mount defenses against the actual pathogen.
Other treatments: Antivirals, since antibiotics don’t work for viruses.
Because viruses are so small, we often get infected without noticing. Especially now that COVID-19 is spreading wildly around the world, it is important to protect ourselves and others from getting infected. Some ways that we can reduce the risk of getting sick are to wash our hands frequently, self-isolate when exhibiting symptoms, avoid going to crowded places, etc. Below is a link with more advice:
Many people suffer because of various infectious diseases, but when we are aware and consciously trying to prevent getting infected, we are offering protection to ourselves, other people, and this world. Stay safe and healthy!
Written by: Benetta Wang
References:
Staff, ScienceAlert. “What Is a Virus?” ScienceAlert, www.sciencealert.com/virus. Accessed 28 Aug. 2020.
“How Infectious Diseases Spread.” Ministry of Health NZ, www.health.govt.nz/your-health/healthy-living/environmental-health/infectious-disease-prevention-and-control/how-infectious-diseases-spread#:%7E:text=Infectious%20diseases%20have%20different%20ways,or%20contaminated%20objects%20or%20surfaces. Accessed 28 Aug. 2020.
“Advice for the Public on COVID-19 – World Health Organization.” ., www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public. Accessed 28 Aug. 2020.
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