The cell's greatest enemy is a microscopic organism called a virus. The battle between these two tiny living entities has great significance for humankind. Some viruses merely cause annoying sicknesses like the flu, but others can lead to deadly diseases such as AIDS and typhoid.
The attack of viruses on cells is typically fatal, but also quite amazing because of their highly advanced techniques. The basic viral strategy is to strike at the cell with its own machinery and weapons. The way a virus makes copies of itself is in a sense, a suicide attack, because to perpetuate on the next generation of viruses, it sacrifices both itself and the cell. On previous pages, you saw how cells, in order to continue their existence, produce proteins according to the information contained in their DNA. Viruses sabotage their host cell's protein production facility and turn it into a factory for replicating new copies of itself.
Lifeless, yet Clever Enemies
One of the strangest organic structures found in nature, viruses do not have a living body, but contain only a genetic mechanism. A virus is nothing more than a genetic code (either RNA or DNA) found inside a protein envelope (See Figure 9.1). It has no organelle or functions that would indicate life. But when it makes contact with a living cell, it virtually comes to life, displays features of a living thing, enters the cell, and in fact becomes an offensive and very clever organism.
A virus uses the cleverest techniques of attack against the human body (See Figure 9.2). Before it enters a cell, it first determines with its leglike fibers whether the particular cell is appropriate for it to enter. If its test comes out positive, it releases its DNA into the cell, which, in effect, means that the "guts" of the virus itself enters the cell, leaving its protein coat behind.
After this initial event, the mechanisms inside the cell are now deceived by the virus. The cell does not identify this new DNA that has just entered as foreign. It is transported to the nucleus, where the cell's own DNA is located. The viral DNA now reaches the nucleus and is incorporated into the cell's DNA. From this point on, the cell begins to replicate the viral DNA, thinking it is just making the cell's ordinary proteins. Unaware of the difference, the cell continues its production of the viral DNA.
Actually it is very difficult for the cell to realize this deception. Differentiating between viral DNA that's become incorporated into the cell's DNA would be like trying to find a sentence hidden on one page of a 20-volume encyclopedia. Thanks to this cunning strategy, the virus can insert itself into the cell's programming mechanism and actually become a part of the cell itself.
It's possible to completely change the meaning of a sentence simply by flipping a phrase or a few words in it. And this is just the type of critical change a virus effects to sabotage the cell's whole production facility and derail it from its original purpose. The viral DNA places itself in a critical location in the cell nucleus, changing the whole meaning of the production code.
Normally, the cell reads no protein codes apart from those proteins necessary to itself. But now, with the viral DNA codes locked into its own, the cell reads both and, literally as if bewitched, begins production. How does the virus take control of the cell's protein manufacturing mechanism, and affect its enzymes, making it copy its own viral code and produce its own proteins? This is still a mystery.
This event prepares the way for the cell's inevitable end. Dying, the cell utilizes all its energy in producing the changed code now present in its nucleus. In the end it dies and is torn apart. The replicated virus, which has virtually sucked the life out of this cell, disperses through the bloodstream to other cells and finds new victims for itself. This viral invasion spreads exponentially (See Figure 9.3).
If it weren't for the body's defense mechanism, this invasion would spread rapidly enough to kill a normal person within a few days. But within a very short time, our defense system realizes that a virus has entered the body and immediately begins a counterattack. Consequently, a person who could otherwise die from a simple cold virus is allowed to survive.
These interesting behaviors of viruses are as thought-provoking as they are shocking.
First of all we need to ask how a virus found in nature can possess the knowledge to invade a human body and take over its cells? For a virus to be able to do this, it must know the human cell intimately, and must be able to find a way to incorporate its own DNA into that of a human being's.
But it's wholly illogical to think that this could happen. A virus is made up of only DNA with an envelope surrounding it. It cannot possess the ability to recognize the human body and change itself accordingly.
Here we are faced with an inescapable truth: A virus has been especially created to enter the human body and insert itself into its DNA.
To use another analogy, imagine that while walking through an empty field, you came across a highly sophisticated door lock and then a little while later, you found a key. If you then put the key in the lock and the door opened, what would you conclude? Would you say, "What a coincidence! This piece of metal opened the lock by chance"? Or would you conclude that the key was crafted to open the lock, but that they had merely been placed in different locations? Being intelligent, of course you would accept the second conclusion.
A virus and the human body have a similar lock-and-key relationship. A virus that has existed in nature for tens of thousands of years with no relationship with a human cell, suddenly enters the body, goes straight to the cell, and opens the lock. First of all, it breaks down the cell wall, because it has been designed to penetrate this wall. Then it integrates with the cell's DNA, because it has been created in such a way that it can do so.
In other words, viruses have been created in order to enter the human body and cause diseases. God willed for people to be prone to illness. Since man is liable to get haughty and proud, only with these types of illnesses can he perceive his weakness and utter dependence on God.
However, while God creates the disease, He also creates its cure. While He has created the virus, He has also created a defense mechanism that puts up a magnificent fight against this virus, which is how mankind can resist so many of the different viruses we encounter every day.
Moreover, God sometimes uses viruses as a cause of death. God determines a period of life to whomever He wills, and this determined period comes to an end when He wills. So a virus is just one of the reasons for death that God employs. Throughout history, millions of people have lost their valuables, their property, their partners, their children-in short, their very lives-due to a virus they could never see. Even though modern medicine is finding cures for many viruses, it is quite significant that new, highly drug-resistant viruses are emerging. Relatively new viruses like HIV and Ebola are continuing to be the causes of death for bodies whose end God has willed, as decreed in the verse "Wherever you are, death will catch up with you" (Qur'an, 4:78).