Understanding Viral Infection

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Massive public concern hits the streets of Mexico, the USA and other Central American countries as over one million reported cases of Swine flu are reported in Mexico with over twenty reported deaths. Swine flu has been know to infect humans in the past, particularly pig handlers but it has never been considered a major threat until now. The virus has now been identified as having crossed the species barrier.

Apparently the virus has been able to form mutations within its capsular wall by including proteins associated with human and avian flu strains. This new mutation makes it challenging for the human bodies immune system to recognize the pathogen and neutralize it.

Although this new virus strain does cause concern, the statistics of exactly how destructive this virus is need to be properly analyzed. Questions which are being asked include, does twenty deaths out of one million people infected with the virus give cause for serious concern? How do these numbers compare with other more common human forms of the flu virus epidemics? Are there any variants from the norm regarding risk groups? Can this new virus strain also be carried by avian vectors?

With H5 N1 bird virus we learned that young healthy people were primarily at risk precisely because of their strong immune reaction. How does this new mutation compare with avian flu ? It is clear that the public need more information about the way that this new virus acts.

It is thought that the virus can be transmitted by a number of vectors including direct contact with pigs, direct contact with infected humans, (the ingestion of infected pork products is stated as not posing a risk because this virus is specific to the respiratory tract), direct or indirect contact with the feces of infected pigs or humans, aerosol spray from the respiratory passages of infected human vectors or contact with surfaces upon which the aerosol of infected humans landed. Water could also serve as a vector if it was contaminated with viral infected feces or respiratory aerosol from infected animals.

On the basis of experience gained from the avian flu and SARS outbreaks authorities are swinging into action to contain the epidemic to avoid the risk of another pandemic and to minimize the risk to citizens of both nations. Citizens in higher than normal risk areas are advised to remain calm but to minimize possible exposure sources where possible by using common sense and to report and to seek medical advice for all flu like symptoms experienced by themselves their family or friends. Washing of hands and avoiding contact with persons showing infection with flu symptoms is advised.

Health experts have been quoted after stating that with the end of the flu season drawing close, it is hoped that this epidemic will come to a swift end.

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How many times have your workers phoned in to you and said “boss, I got a virus. I can’t get off the toilet”? During the summer months especially it seems as though somebody is taken ill by a virus every week.

I usually asked them to bring me a doctors note and let it at that. Force major, what can you do? It seemed like I was the only one who never got sick. Could it be that responsibility is the best prophylactic medicine around? I always added “come straight in as soon as you feel well. Even though I knew that this was not the best thing to do. Soon you’ll understand why even if this statement confuses you right now.

The doctor usually always tells you the same thing. “yes you’ve caught that virus that’s been going around. Take something to reduce the fever, stay in bed for three days and drink plenty of water”. We all know that a virus is a variety micro organism that has the ability to infect us with several types of very unpleasant types of illness. The most common of these are upper respiratory tract infections and stomach infections. Other viruses which are less common in the western world due to attention to public hygiene issues include pneumonia, viral meningitis, viral pneumonia, hepatitis A, B and C, polio, several forms of zoonotic encephalitis, yellow fever, dengue fever, western Nile fever, rift valley fever, ebola disease, colorado tick fever, machupo, junin, rabies, small pox, various forms of cancer causing viruses and HIV to name but a few. All of these are very serious life threatening illnesses. Some viruses produce conditions which are considered mildly uncomfortable such as mouth ulcers, foot and mouth disease, cow pox and common warts, to mention just a few. There is a whole other range of diseases that are termed as childhood diseases which are also of viral origin. These viral conditions include measels, german measels chicken pox, mumps, and whooping cough. Some of these are included in inoculations against the contraction of dangerous disease during childhood and some are left to the course of nature. Viruses also impact animals and plant species with often serious financial impact. Dog parvo virus is the most resilient of all viruses.

Scientists were divided in their opinion on whether it was correct to classify viruses as living organisms because they have no metabolic function as such. Viruses in simplistic terms are made up of a proteinous outer shell, proteinous genome material, enzymes and sometimes lipopolysaccharide (fatty) outer structures . All viruses are host specific but are not only host specific but are parasitical only to specific organs of the host. Rabies virus travels only along the tissue of the nervous system and will not attack the cells lining the intestine or the blood tissues. The virus that causes the common cold will not cause hepatitis and so on.

The following clip explains the path of avian flue infection. Remember that although viruses all have slightly different ways of getting into and out of living host cells the bottom line is that they all have the same objective and basically do the same thing.

All viruses enter the body via a vector. That vector could be organic material contaminated with feces, it could be via infected water or it could be introduced into a recipient body by body fluids such as saliva or sperm or it can be transferred via mosquitos or ticks. A virus is a really just a mechanism for replicating itself and it does this in the following manner. All viral invaders must breach the cell wall of the host cell and empty the contents of the viral body into the host cell. After doing this the virus activates its genetic material, each in it’s own way, to insert DNA or RNA into the DNA or RNA of the recipient which it then uses as a template to manufacture duplicate strings of DNA. The strings of DNA are then used to transcribe a code for the production of proteins which will be used to manufacture duplicate viruses within the recipient cell.

The recipient cell will cease to function as a useful cell of the body which may or may not stimulate an immunological response by the organism. When the cell wall has swollen to proportions it can no longer tolerate it will burst and the newly manufactured viruses within will flood into the organism and infect more cells. The condition in which the body is swamped with these newly released viruses is known as viremia. During the period in which the virus is initially infecting the body there is usually no immunological response. This is due to the fact that all the process is being carried out within the cell and the immune response of the body is slow to pick up on this in the initial stages because viruses can go undetected by immune cells if they have undergone some form of mutation which makes them apperar differnt to the imunological memory cells.

When the body starts to be flooded with newly developed viruses the immune response will be triggered and the host and symptoms will appear. The period of time between infection and the manifestation of symptoms can be anything between several hours in some cases to several years in the case of some retro viruses such as the HIV virus. Some viruses will insert their DNA into the DNA structure of the host and encode it to remain dormant. All of us have a certain percentage of dormant viral DNA mixed in with our own DNA. This is termed as Junk DNA. Only under very special conditions will this DNA be activate to begin the manufacture of replica viruses.

Viruses that infect the small intestine typically target the epithelial cells which coat the villi. When this happens the affected areas of the intestine will cease to absorb nutrients from the food. The food will remain in liquid form to which the liquid content of the cells is added on rupturing. In addition more liquid from the non specific immune system is added and the food is evacuated as what we recognize as diarrhea. Viral intestinal disorders can be accompanied with vomiting, nausea, headache and increased temperature. All of these symptoms are part of the bodies strategy to clear itself of the viral invader.

The swelling of the cell wall and its bursting under the pressure of the newly developed virus within is known as Lysis. Lysis is the destruction of the cell due to internal causes. During this process ulcerated and painful lesions may be formed in infected tissue. When these burst the viruses are released into the blood stream causing viremia. This destruction of cellular tissue can be accompanies by the presence of blood in stools. Loss of blood in stools is a case for medical supervision because the amount of blood lost may well have to be replaced by blood transfusion.

Viral infections of the intestine can last anything from a day to several weeks and vary in intensity. A long lasting infection may be severe of mild. It all depends on the virus in question and if the bodies defenses have any memory of this virus or viruses with similar protein structures on the outer wall. Some short lived infections can be extremely unpleasant and in contrast they can be very mild. There are no set rules. Viruses change the structure of their cell walls through mutations. This is part of the evolutionary success of viruses. The sheer numbers by which they replicate themselves leaves every statistical possibility for viral mutations to occur.

This video of the production of the HIV Retro Virus is a good animation of how viruses use host cells to transcribe the proteins that they need to reproduce themselves. In oter types of virus the process is simpler but basically the same.

The only sure way to protect yourself against entero viruses is to maintain a good personal hygiene regime in the home and at work and to buy food from a safe reliable source and to make sure that you have a safe water supply..

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