Virus Types – A Brief Introduction

What is a virus? A virus is simply an infectious agent which can only multiply within a living host organism. Viruses may infect various types of living organisms, such as plants, animals, and humans. They have a simple viral structure so that a simple microscope is required to see them.

In order to understand how a virus spreads from one cell to another, it’s important to know that each type of virus is unique in its DNA and its ability to multiply and reproduce itself. The envelope protein (or capsid) of a virus is made up of a pair of DNA sequences. One of the sequences is replicated in the host cell and the other is passed on by the host cell to the next cell along the viral chain.

Every virus is a combination of components such as protein, DNA, ribosome, plastic etc., with a pair of chromosomes encircling it. The virus’ envelope is made up of two membranes – an envelope vesicle and a cell membrane. The envelope membrane is coated on both sides with a protein coating that makes it more water-resistant than the virus cell. The envelope membrane is also designed in such a way that it will latch onto any cells that are in the area of the “hot spot”. Hot spots are areas of infection where there is high population of a particular type of disease-cells.

The most common of all viruses is the herpes simplex virus, which is responsible for approximately 50% of all cases of viral arthritis. There are other very common viruses too, such as the Epstein-Barr virus, Q fever, hepatitis B, retroviruses, Epstein-Barr virus and even bacteria like E. coli. Some viruses are able to cause a wide array of symptoms in a specific set of organisms or in a single, specific infection. Some examples of these types of viruses are: shingles, hepatitis, Epstein-Barr virus, Varicella-zoster virus (Vesicloviridae), herpes simplex virus (HSV), Epstein-Barr virus, meningococcal meningitis virus, hepatitis B virus and viral encephalitis.

Many people are quite surprised to know that there are some viruses that produce no symptom at all in animals such as the rick fever bacteria and the Lassa virus. Some examples of organisms that are completely harmless are bacteria like E. coli, Streptococcus salivarius, Lactobacillus acidophilus, Gardnerella angustifolia, Staphylococcus aureus, Staphylococcus antifungus and Streptococci spp., all of which are entirely non-susceptible to man. Other viruses are the ones responsible for producing symptoms in humans like the hepatitis B virus, hepatitis c virus and Epstein-Barr virus. These are very contagious, thus facilitating the spreading of the diseases. In fact, some types of viral infections are responsible for generating more serious ailments including cancer.

The type of virus that is generally lethal to most of the living cells and organisms is the retrovirus. These retroviruses are produced by a kind of cell called the retrovirus, which remains inactive in other cells until it produces a favorable condition for reproduction. When the retrovirus is activated, it invades the host cell, copies itself into various parts of the DNA structure, produces a messenger RNA or mRNA for further replication and causes the termination of the genes programmed by the genes for the protection of the host cell from the invading virus. From this point on, it replicates itself endlessly without any controls and the invading viruses can seriously damage the host cells, tissues and organs. Examples of retroviruses are the retroviruses that cause AIDS and lymphoma. HIV is another retrovirus that causes Acquired Immune Deficiency Syndrome (AIDS) and is responsible for the immune suppression syndrome that characterizes AIDS.