What is a Virus?
In the last few months, three viruses have gripped our attention. The influenza virus because of a few weeks of possible flu immunization shortage, the emergence of the Enterovirus D68 a summertime virus that turned into a real attack on the breathing system, and of course, the Ebola virus.
And, of course, we all know about colds. Everyone gets them, they cause so much agony, and they are so common.
All these, and many other infections are caused by a very peculiar type of life, the virus. So we thought it might be interesting to present in a little more detail what is a virus.
The Basics- what's in a virus, how do they work?
Viruses are the simplest and one of the oldest forms of life. Other forms of life include the bacteria, the yeasts and fungi, the animals, and the plants. All these forms of life consist of either single cells (bacteria, yeast), or groups of cells (fungi, animals, and plants). But not viruses. Viruses are the only type of life that has no cell. Because they are not cells, some even wonder if they are really alive.
But all agree that viruses can reproduce and adapt, so by that skill many consider them very much alive.
Viruses are also a very old form. They are at least several billions year old. Compare that to the current human line, which at most is 150 thousand years old. No comparison.
Viruses do reproduce and change, but can only do so using some other form of life's cells. No cells, no viruses. Without their own cells, how do they reproduce and evolve?
The answer is very interesting. They are actually packages of information. Every virus has a bit of genetic material (DNA or RNA) inside, wrapped in a protein coat.
The protein coat picks the lock to the cell that virus can infect. Once inside, the protein coat then delivers its inner contents, the genetic core, to the cell's genes. There the virus takes over the cell's machinery and forces it to spin out a huge number of copies of the viral genes and their protein coats. In this way, one virus in one cell can lead to the creation of a staggering number of new viruses, ready to repeat the cycle over again.
Why Viruses are Often so Specific to One Type of Life
So this means that to live, a virus has to find a way into a cell, and a way to go from cell to cell. This is no mean feat, in fact it is astounding. It is so challenging, that with few exceptions, every virus can only get into the cells of one species.
The cold virus for a chicken can only give chickens colds. Measles virus can only give humans measles. Other viruses can only infect certain bacteria, others only one species of plant, and so forth.
There are also viruses that have figured out how to crack the code of various species, usually on type of life. So there are viruses that can infect several animals. But there are few, if any, that can infect various animals and plants.
Perhaps the most prolific virus is the influenza virus which infects nearly all humans during the winter, but only infects animals in the spring and summer- usually barnyard animals and birds.
How do Viruses Make us Ill?
The answer to this question has two answers:
1. Viruses destroy cells
2. Viruses change the function of cells
In many of the most common and mild viral illnesses, like colds and flus, viruses actually destroy the cell they use to reproduce. Remember that the way all viruses work is that their genetic material takes over the host cell gene machine and forces it to make copies of the viral genes, to make more viruses. If in that process a zillion viruses are copied, the cell often pops from the expansion, and dies, releasing the zillions of viruses. This kills the cell. If enough cells die, then a patch of tissue is left destroyed and inflamed. This is what happens to your nose when you get a cold. It really is very much like a mild burn, the lining of the nose gets destroyed by viruses popping sheets of cells.
Any viral infection like this makes us ill by literally burning away a sheet of cells, causing pain, inflammation (this is where fever comes from), and lost of fluid leaks (runny nose, vomiting, diarrhea, for example)
Sometimes, though, the cell is not exploded from rampant viral copying. In these situations, the virus still takes over the cell's gene machine, but the virus has it create an ongoing production line of viruses, not enough to pop the cell, so the cell continues to live, but it stops working normally. The most famous example of such an infection is AIDS, where the cells of the immune system are infected but not destroyed. In many ways, we are better off with viruses that kill cells, especially if they are superficial cells, for then the body makes new, healthy cells to replace the dead ones. But if the cell lives and lives well enough, it will continue to work (even if abnormally) and this can cause much and long-lasting dysfunction and trouble, as in AIDS.
And then, some viruses can lie dormant for years. They insert there genes into the host cell and then just sit there and do nothing. In this situation the person is not ill, but if the virus kicks on and starts making tons of copies at some point, an illness could erupt. This is the story of chickenpox and shingles, where once the chickenpox illness is over, the same virus just sits dormant in the cells near the spinal cord. Every now and then they reactivate, travel down the nerve to the skin and this is shingles.
How do we Recover from a Viral Illness?
The only way our body can recover from a viral illness is to kill every cell that is actively infected with a virus. We can't actually kill a virus since on its own it is hardly alive. But if our body kills every cell that contains a certain virus, then that virus will be cleared from our body. This strategy works only if the body can identify every cell containing that virus and kills all of them.
And, this is exactly what happens in colds and flus. Our body goes after every infected cell, and the infection and virus is completely eliminated, new cells are made to take the place of those destroyed by the virus, and we heal.
If our body cannot do this, the viral infection becomes chronic, like AIDS, and many hepatitis viral infections.
And, in the case of dormant viruses, the body leaves these alone, the cells that contain the virus look no different from normal cells because the virus is not doing anything, so the infection is lifelong, but dormant, like dormant chickenpox that simply sits there unless a shingles flare occurs.
How do We Treat Viruses?
A handful of viruses can be cured by treatment with anti-viral drugs, viral antibiotics.
These include influenza, hepatitis C, and some herpes viruses such as CMV and herpes simplex.
In each of these examples, the drugs do help, but are not 100% effective.
But, for nearly all other viruses, there are simply no drugs that actually kill the virus, speed up the healing from all the havoc they cause, or even end the symptoms they create. This is most vividly experienced with common colds and stomach flus, where drug stores have shelves bursting with products promising an end to runny noses and coughs, or diarrhea, but always fail to deliver. At this time about 500 drugs promising relief from viral symptoms are under investigation by the FDA for false claims. Five hundred such drugs under investigation!
Two viral symptoms that can be treated by drugs are fever and pain, and we recommend ibuprofen (Advil, Motrin) over acetaminophen (Tylenol) due to questions about whether acetaminophen may boost the development of asthma.
How do we Prevent Viral Infections?
We are all strongly drawn to the idea that if we simply take this or that action, we can stop the spread of viruses through a classroom, school, or home. The evidence, however, is overwhelming that viruses travel from person-to-person astounding well, despite kids being kept home when ill, despite hand-washing, despite nearly any effort. Just looking at the sweeping waves of viral infections that cover continents in a matter of days dramatizes the fact that trying to stop a virus from spreading, especially common, very contagious ones, is like trying to stop the wind.
Given that very few viruses can be treated, and none of the very contagious ones can be stopped from spreading, that leaves us with only one control measure that has had any real impact- immunizations.
The body has figured out how to protect itself in one of the great triumphs of clever evolution, one we recover from a virus, it is almost always the case we cannot get it again. If you get measles, you never get it again. If you get cold variety #281, you never can get sick from cold #281 again (of course, you can still get cold #282).
This very natural, very important key to our survival is the whole basis of the idea of immunization. If you can't get a viral illness twice, why not deliver a very mild case of that illness, so when the real thing comes along, you can no longer get it.
Do immunizations work? Just take a look around. Smallpox in the 20th century killed 500 million people, more than World War I, World War II, the Korean War, and the Vietnam War, and all other wars in that century, combined. But because of immunization, and only by this strategy, smallpox is now eliminated from the planet. It worked.
And, it has worked in every case- measles, mumps, rubella, even chickenpox, hepatitis B, polio, all are sharply reduced. In areas where immunizations are used by nearly everyone, these diseases are essentially eliminated.
Bottom Lines
1. Viruses are curious packages of genes wrapped in proteins. The proteins gain access to the target cell, the genes make the cell make more viruses.
2. In destroying the cell, the virus causes the illness. When sheets of cells are destroyed, the illness is where the irritation takes place- runny nose in the nose, sore throat in the throat, cough in the lung, diarrhea in the gut.
3. Only a small number of viruses can be killed by a medication, almost none of their symptoms can be relieved by medication.
4. It is next to impossible to stop the spread of a very contagious virus. Some viruses are quite rare and do not spread well, and these are the very, very rare examples of viral infections that can be controlled by containment (e.g., SARS, Ebola).
5. The only action that has ever really spared us from the diseases caused by viruses has been immunization, which has had a spectacular and dramatic record of success.
To you health,
Dr. Lavin
*Disclaimer*
The comments contained in this electronic source of information do not constitute and are not designed to imply that they constitute any form of individual medical advice. The information provided is purely for informational purposes only and not relevant to any person's particular medical condition or situation. If you have any medical concerns about yourself or your family please contact your physician immediately. In order to provide our patients the best uninfluenced information that science has to offer,we do not accept samples of drugs, advertising tchotchkes, money, food, or any item from outside vendors.
