Viruses are tiny microbes living within our environment. Their simple structure comprises either RNA or DNA — a genetic material with a coated protein layer. While their structure is simple, their categorization is a bit complex. Viruses are neither living nor non-living creatures. They are activated only when they have infected a potential host cell; otherwise, it is safe to assume them dead. This is also one of the reasons viruses do not fit in any phylum or kingdom in biology.
There are multiple theories of the origin of viruses. According to scientists, viruses are a result of billions of years of evolution. According to one hypothesis, viruses are the reason human life came into being — as a result of a cell enveloping a virus. While there may not be an exact number of years to show when viruses came into being, it is a fact that viruses are now an integral part of our lives.
The working of viruses varies from virus to virus; therefore, in this blog, I will be giving a general overview of how viruses work coupled with detailed descriptions of two contagious diseases caused by viruses: Ebola and COVID-19.
How Viruses Work:
As mentioned earlier, viruses cannot move or act without infecting a host cell. But once a virus attacks a host cell, it can multiply and reproduce rapidly. Viruses only target those cells with which their receptors match. Receptors on a virus’s surface decide and guide the virus what kind of cells to target. For example, when people are infected with the SARS virus, one of the first signs that confirm that one is infected is cough or bad throat because the SARS virus has receptors that only match with the cells of lungs; therefore, it only attacks the lung cells — known as alveoli. On a molecular level, viruses do not know much, but their biological binding helps them navigate. Once the virus gets inside a cell’s genetic material, it hijacks its cellular machinery and starts replicating and reproducing.
There are many types of viruses that keep themselves hidden or lay dormant in the human body and work silently. They only come out when enough damage is done. In fact, it was not until 2018 that the scientists discovered that viruses could form into membrane-bound packets or spheres. These membrane sacs act as a “Trojan horse” to pass through the body’s defenses.
One such virus is that of Ebola, which I will now further expand on.
The Ebola Virus:
The deadly Ebola virus first broke out in West Africa. It belongs to the family of filoviruses called Zaire ebolavirus. The Ebola virus is considered deadly because of its high mortality ratio, which is the result of its unique way of attacking the human body. Once the Ebola virus has entered the human body, one of the first tasks it does is disarm and weaken the human body’s immune system. Once the immune system is weakened, it starts replicating itself by hijacking the cellular machinery.
As mentioned, when a specific virus enters the human body, it generally has receptors that only match with specific organ cells. However, when the Ebola virus enters the human body, it starts with infecting the dendritic cells of that body — whose prime task is to display signals on their surfaces to activate T — lymphocytes, the white blood cells that could destroy other infected cells before the virus replicates further. Generally, viruses do not attack the immunity cells, which is why it is easier for the WBCs to fight them. In the case of Ebola, because the virus infects the dendritic cells, the infected dendritic cells cannot send signals to the lymphocytes and other antibodies to activate the immunity, which allows the Ebola virus to start replicating itself. The lymphocytes themselves are never infected by the virus; other factors such as the lack of stimulation and signaling prevent them from picking up a fight.
As the Ebola virus starts going to different body sites by means of blood, it is eaten by other cells of the immune system known as macrophages. The corrupted macrophages then release proteins, which attack the vascular system of the human body. This results in the formation of small blood clots throughout the human body’s vascular system, resulting in significant problems in supplying blood to the organs. One of the factors that make Ebola deadly is that it does not trigger a specific organ, except its influence on the liver is the most severe. But its system-wide inflammation and fever destroy many tissues and cells, which adversely affect the blood vessels, causing leakages in them. This eventually causes hemorrhaging — internal bleeding — in the human body. Moreover, in the case of Ebola, giving messages to working cells to commit suicide is also very common. It is pathogens manipulating cells, also known as programmed cell death.
When the virus has done more than enough damage in the human body, the immune system gives it a last shot by launching a cytokine storm. It is an SOS system that causes the immune system to launch all of its weapons. While it manages to curb the virus’s impact, the cytokine attack also destroys most of the cells in the human body. People with better immune systems face the most damage in this case. What eventually kills an Ebola patient is the vascular damage, drop in blood pressure, and multiple organ failure.
The Ebola virus is contagious. Ebola virus spreads through one’s contact with infected human feces, vomit and blood.
The Coronavirus — 19:
Another example to know the workings of a virus in real life is that of the infamous COVID-19. The months-old novel coronavirus that affected the entire human civilization is a virus that first broke out in China and has now shaped into a pandemic by spreading in 215 countries.
SARS-CoV-2 is a virus that causes respiratory illness. The pathogen of the COVID-19 belongs to the family of coronavirus — the same family that includes viruses like SARS and MERS. Each virion — singular particle of the virus — is made up of RNA with a protein coating. The COVID-19 virion has spikes coated with a layer of lipids and fat. Its spikey surface made up of fat is the reason alcohol soaps or sanitizers can protect you from getting infected because fat and lipids dissolve in alcohol.
Now, how does the COVID-19 spread or attack the human body? When a virion of coronavirus attacks a cell, it releases some chemicals that adversely affect the cell membrane, fuse it and eventually corrupt it. This allows a virus’ RNA to enter the cell and start working.
The virus then hijacks the protein-making cellular machinery and prints the copies of its own RNA. In the matter of some hours, the cell is manipulated into making thousands of copies of the COVID-19 virion, which start attacking other healthy cells.
However, since the COVID-19 is less deadly than the Ebola virus and does not directly infect the cells of your immune system, people with robust immune systems are likely to recover from the COVID-19. Moreover, since this virus causes respiratory illness, it affects the lungs the most.
With most viral infections, the body temperature rises in an effort to curb the virus or kill it. This also allows the WBCs to kill the virus and create more antibodies for maximum protection from any organ failure or adversity.
However, people respond to COVID-19 differently. For example, it is easy to get over and fight against if only the upper respiratory tract of the human body is infected. If the virus somehow manages to infect the parts below the vocal cords, it can result in severe breathing problems. The temperature rise is one way for the human body to fight against the virus; however, prolonged and consistent high temperature may result in bodily damage.
The COVID-19 easily transfers from human to human through direct contact and by means of droplets when an infected person sneezes or coughs. It is also spread by means of fomites.
So, by now, you must have had some idea of how viruses work. What makes viruses unique is their mechanism. A virus itself does not interfere in the bodily functions at an extensive level; all it does is hijack the cellular machinery and then start replicating itself. Moreover, most viruses — like the Ebola virus — do not render you problems themselves.
They weaken your immune system, which allows other bacterial diseases to attack your body in different ways. Once your body has fought with the virus, the opportunist bacterial infections take advantage of your weakened immune system. This is also one reason the elderly, and children were initially considered the potential targets of the COVID-19. In conclusion, it starts and ends with your immunity.