VIRUSES are simple life forms consisting of nucleic acid, encoding genetic information, and surface components of protein that enable them to enter cells. Unable to multiply outside of living host cells, they are completely dependent on these cells for their continued maintenance. Viruses utilize the metabolic machinery of the cell and have the ability to interfere with, or direct in an adverse fashion, the activities of the cell. MUMPS, MEASLES, GERMAN MEASLES, and CHICKEN POX are common childhood illnesses caused by viruses. The common cold is usually due to the rhinovirus. The "flu" or the "grippe" is caused by INFLUENZA viruses. HEPATITIS, an inflammation of the liver, may be the result of one of several viruses. Rabies, yellow fever, and Lassa fever are highly lethal viral diseases.
Technically speaking, a virus is not even alive. A living organism contains all of the genetic material necessary to reproduce itself. A living organism consumes food and excretes waste. A virus does not do any of these things. The free virus particle, or virion, consists of NUCLEIC ACID -- either DNA or RNA, depending on the specific virus--surrounded by a protein coat, or capsid, and, in some viruses, an outer envelope of fats and carbohydrate. Both RNA and DNA are necessary for a virus to be able to reproduce itself. The outer coat of the virus had certain protein characteristics that give each separate species and strain their identity.
Virus reproduction begins when the vision comes into contact with a suitable host cell. The virus must interact with a receptor on the cell surface. Animal viruses are engulfed into host cells by interaction of the virion with the host cellular membrane. A process called uncoating releases the nucleic acid from its coat, and the nucleic acid either stays in the cytoplasm, as in the case of some RNA viruses, or travels to the nucleus. The uncoated DNA or RNA begins to function as genetic information by directing the synthesis of specific types of proteins that have enzymatic and structural roles. The infectious cycle usually consists of two different stages. In the first the proteins are produced that are required for the reproduction of the viral DNA or RNA. In the second stage proteins that make up the virion are produced, and these combine with the DNA or RNA to form mature virions, which are then released from the cell.
Viruses were first discovered about the turn of the century in plant species. Their ability to produce human diseases was not appreciated until the late 1930's and 1940's although diseases in cattle had been demonstrated as early as 1898. Research into viral causes of human disease did not occur until the mid to late 1940's when techniques of growing them in animal hosts were perfected. The discovery of antibiotics in the 1940's gave false hope that these organisms like bacteria could be controlled and cured.
Since a virus has to have an animal or plant host to reproduce, the patient is part of the life cycle. Bacteria are free living plants. They are capable of living outside the confines of a host. They are able to live on biologic media, use it as a food supply, and thrive while viruses do not. Viruses do not take in substrate (i.e. they don't eat) therefore the antibiotic is not absorbed. Secondly, since the animal cell is part of the life cycle, any drug that affected a virus would necessarily affect the host animal cell. In Pediatrics, that is usually someone's child.
How do I get a virus?
When a virus invades a host body, the repeated invasion and destruction of cell, give rise to multiple symptoms and the body's natural ecology is disrupted. This cycle will continue until the body develops its own antibodies to defeat and kill the viral invaders. Once the virus is defeated, the body will continue to make these antibodies so the infection cannot happen again. Usually, a person never gets the same strain of a virus again. For example, once a person has had a case of chickenpox, he will never get it again. This is the principle of vaccines. Each vaccine causes a very mild case of the disease so antibodies are produced. There are hundreds of viral strains and sub strains in the environment, and each one is a separate disease although they usually have the same symptoms.
In the last part of a viral life cycle, the host cell breaks up. At that time, literally millions of mature viruses are released ready to begin the process over and over again. In the process of this life cycle, the body releases compounds such as HISTAMINE that cause a number of reactions. The illness can range from a simple runny nose, to pneumonia, to viral meningitis. Secretions coming from the nose, lungs, urine and stool all contain millions of viral particles. If a person is in close contact with these secretions and has not previously had that strain of virus, he will catch the disease. Hand washing and secretion avoidance are the ONLY ways short of a vaccine to avoid catching a virus.
The current state of our American lifestyle is such that both parents work outside the home more often than not. The children are placed into Day Care where they interact with children their own age. Toddlers, enjoy touching and placing things in their mouths. All too often, one child with a cold at the day care will wind up infecting the entire group. It is the clear runny nose that is the most contagious not the green congested child with a fever (he is usually sent home by then). Sneezing aerosolizes the secretions and sends them scattering across the play space for all to inhale. This is why children in Day Care, whether public or private, seem to stay sick all the time and average 6-10 colds a year.
How do I treat a virus?
Antibiotic classification systems are based on whether an antibiotic kills microorganisms (bactericidal effect) or merely inhibits growth (bacteriostatic effect). Bactericidal means just what it sounds like. The bacteria are killed by the disruption of their cell wall. When susceptible bacteria are exposed to bacteriostatic drugs, growth will cease temporarily and then resume allowing the body's own immune system to destroy the bacteria. Since the life cycle of a virus does not use these methods to reproduce, treating them with antibiotics is impossible. It just makes the patient at risk for "SUPER-BUG" bacteria that do not respond to any antibiotics at all due to over prescribing.
The patient can only treat the symptoms that make him uncomfortable until the virus has been defeated by the patient's own immune system. There is no medication currently that will shorten the life cycle of the common virus. Antihistamines and decongestants are all that are available as therapy at this time. Once the infection has subsided, the body's natural immune system will generally keep it safe from future infections of THAT strain of THAT virus. There are hundreds of separate diseases, however, all with the exact same symptoms.
What can be done?
The only means of controlling viral infections is prevention by isolation and hygiene. When your toddler comes down with a cold, DO NOT take him to Day Care unless proper isolation measures exist there. If you do, he will spread the infection through the entire class. He will also catch a similar virus if HE is well and ANOTHER child with a clear runny nose shows up that day. Ideally he should not return until the cold is over which is usually about a week. It really takes a good neighbor policy between day care parents to prevent the spread of an epidemic through the entire school. In day cares where this policy is enforced, the entire population is seldom sick and fewer work days among the parents are missed.
Older children must have the importance of hand washing stressed to them and sufficient supplies of soap, water, and towels should be available. The importance of not drinking or eating after an infected person should be stressed.
In spite of efforts by the scientific and lay press, many people still cling to the misconception that antibiotics will cure a cold and that bacteria are behind every illness. There is absolutely NO REASON for an antibiotic to be given to cure a common cold. The doctor may prescribe one if he or she feels that the child is at increased risk for secondary infections depending on the diseases going through the community or the child's clinical history, but that should be his or her call. That is why antibiotics are not sold over the counter as they are in Mexico and other third world countries. The current problem with FLESH EATING BACTERIA and other resistant bacteria stemmed from Mexico where the bacteria have developed defenses against over used antibiotics sold in every store. When used improperly, antibiotics cause MORE HARM THAN GOOD.
Some parents will start left over antibiotics when their child has a fever and the doctor is not readily available. They feel that they must 'do something'. This is the worst action that can be taken. When seen, if it is necessary to obtain blood, urine, throat, or even spinal fluid cultures by the doctor, the cultures will be negative due to the antibiotics and the doctor will not be able to obtain needed data to treat your child. This can mean many extra costly days in diagnosis and more importantly might put your child in danger. ALWAYS throw away left over antibiotics and resist the temptation to use them.
The best approach to a cold is to watch it for the first three days. Most viral fevers last 48 to 72 hours. There are exceptions to this rule, but for the most part three days is right. If the fever responds to Tylenol, Motrin, or Advil and the child is not acting sick, wait three days and treat with over the counter cold preparations. If the fever is very high or the child acts TOXIC (extremely ill) then a sooner visit to the doctor is warranted. Within those guidelines, a visit to the doctor may not be needed at all.
Portions of the text are from the Grollier Multimedia Encyclopedia 1996.