VIRAL INFECTION DISEASES

AIDS

Most researchers believe that HIV originated in sub-Saharan Africa during the twentieth century. HIV is now a pandemic, with an estimated 38.6 million people currently infected by the disease around the world . The Joint United Nations Program on HIV / AIDS (UNAIDS) and World Health Organization (WHO) estimate that AIDS has killed more than 25 million people since it was first recognized the June 5 1981, becoming one of the most destructive epidemics in history.

Ebola

Several highly lethal virus pathogens are members of the family Filoviridae. These are filamentous viruses that cause viral haemorrhagic fever, including Ebola virus and Marburg virus. The Marburg virus attracted the attention of the press in April 2005 by an outbreak in Angola. The outbreak began in October 2004 and continued in 2005 and was the worst epidemic of any kind of viral hemorrhagic fever.

VIRUSES AND DISEASES

Examples of common human diseases caused by viruses include the common cold, flu, chicken pox, polio, measles, mumps and rubella. Among the major diseases are caused by the Ebola virus, AIDS, avian flu and SARS. Other diseases are polio, mumps, rubella, hepatitis B, hepatitis C, yellow fever, dengue fever, smallpox (eradicated), and so on. Some diseases are under investigation to determine if they have a virus as the causative agent, for example, human herpesvirus-6 (HHV6) could be related to neurological diseases such as multiple sclerosis and chronic fatigue syndrome. It is also investigating whether the Borna virus, which causes neurological disease in horses, could be responsible for psychiatric illness in humans.

The relative ability of the virus to cause disease is described in terms of virulence. The viruses cause disease in the host through different mechanisms that rely heavily on the kind of virus. The mechanisms at the cellular level include mainly the analysis and subsequent cell death. In pluricellular agencies, if enough cells die, the whole body will start to be affected. The virus may also exist within a relatively ineffective body. This is called latent and is a feature of herpesvirus including the herpes simplex virus, which causes cold sores, the Epstein-Barr virus, which causes glandular fever, and varicella-zoster virus, which causes chickenpox. The chickenpox virus, after the disease returns in later life as shingles.

Some viruses can cause chronic infections, in which the virus is still replicating in the body, despite the host's defense mechanisms.This is a common infection of hepatitis B and hepatitis C. People chronically infected with hepatitis B virus serve as reservoirs of the virus (are carriers). When there is a high proportion of carriers in a population, it is said that the disease is endemic.

THE VIRUSES ORIGIN

The position of the virus as a boundary between the living and inert posed to the scientists the problem of its origin. The origin of the modern virus is not entirely clear, perhaps a single mechanism can not answer this question. Since not fossilized, molecular techniques are the most common methods used to hypothesize its origin. Two main hypotheses exist today: The virus would be the first beings in the history of the evolution of the inert to the living, who managed to meet effectively the functions of replication, transcription and translation. Would, therefore, agencies less advanced . The fact that viruses can only do these three vital functions inside living cells, leads to believe the virus could not exist before the emergence of the first cells, no matter how simple they were.
Viruses with only a few genes could be parts of nucleic acid from the genome of an organism. Their genetic material could have been derived from genetic elements transferable, such as plasmids or transposons, which can go in and out of genomes. [47] New virus could emerge at any time, and therefore do not always have the virus ancestors. Viruses with larger genomes, such as poxvirus, may have once been small cells that parasitized cells bigger. Over time, they could not lose the genes required for its parasitic lifestyle in a simplification process known as retrograde evolution. Rickettsia and Chlamydia bacteria are living cells that, like viruses, can be played only within a host cell. The parasitic lifestyle of these agencies has resulted in a loss of genes that in the past would have allowed them to survive outside the host cell. These examples lend credence to the hypothesis of simplification.
The discovery of other forms acelulares has brought new light to the origin of the virus, but has not served to resolve the dilemma posed. The other forms acelulares are:

The proviruses.

Plasmids.

Viroids.
Some scientists (like Temin, in 1969) have postulated that the virus would be the result of the evolution of these forms acelulares: DNA viruses come from proviruses and plasmids, and RNA in viroids. CAPS of the virus would be an evolutionary achievement for which the genetic material would be protected as they move from one cell another, and ensure the success of the infection. On the other hand, forms acelulares could have been born within the cell half, when certain genes to achieve autonomy for the operation of cellular genome, in this way, the origin of the virus would not necessarily linked to episodes that come with emergence of life on earth. But it could also speak of a reverse process: a loss of the Fund to reduce the autonomous units of replication-transcription-translation to the condition proviruses, or plasmids viroids. In conclusion, the discovery of acelulares simpler forms that viruses helps us to better understand their nature and biological significance, but it keeps us on the question of whether we are compared to the first organisms emerged from inert matter, or to form resulting degressive the expertise to parasitism.

CLASSIFICATION OF VIRUS.

The virus has been classifying the type of nucleic acid content, the characteristics of the jacket of the virion, where it exists, the taxonomic position of their guests, a pathology that produce, and so on. Combining characters as those listed, and in that order of importance, have been acknowledged several dozen groups of viruses internally well defined. Taxonomically, due to the absence of fossil record, its lack of autonomy for development and its likely polyphyletic nature, it is very difficult to consistently apply the criteria for classification and nomenclature that served so well for the classification of cellular organisms, or Real bodies. The virus does not easily fit into any of the areas of biological classification, and ranking begins in the range of family or order. Not all families are currently classified under orders, not all genres are classified into families. However, it has been suggested the domain name Acytota (acellular), which would put the virus on a par with domains of life: Bacteria, Archaea and Eukarya. The effort required to reach a natural classification, has produced different results, which we consider here two, the classification of Baltimore and the International Committee for Taxonomy of Viruses (ICTV).

Classification of Baltimore.
The classification of Baltimore distributes the virus in seven key groups depending on the chemical basis of the genome and the mechanism of mRNA. All viruses must generate positive chains of RNA from their genomes to produce proteins and to replicate themselves, but they use different mechanisms in each of the seven groups:

• Group I: bicatenario Virus DNA (dsDNA or virus). The virus DNA double chain entering the cell (regardless of the mechanism of infection) and RNA polymerases do not distinguish the cell's genome virus genome, forming mRNA, which translates into ribosomes and gives rise to proteins of CAPS, and sometimes enzymes replicated. Viruses are simple and can cite as an example to the number of phage T pair, who were the first to be discovered.

• Group II: single-Virus DNA (ssDNA or virus). His DNA is the genetic material of a string of positive nature. Since it is of positive polarity, you need a chain refusal to be able to transcribe, so upon entering the cell the DNA polymerase (enzyme repair or elongation) makes a DNA bicatenario used to synthesize (from the thread negative) an mRNA which carries the information necessary to produce enzymes and capsómeros replicated.

• Group III: bicatenario Virus RNA (dsRNA or virus). RNA viruses carried as bicatenario part of a virion transcriptase which is a viral RNA-dependent RNA polymerase that used to, from the negative strand RNA bicatenario, making the mRNA. Besides being a structural protein is an enzyme, which is part of CAPS, therefore only be replicated if the Fund enters the cell next to the virus genome.

• Group IV: Virus RNA single-positive (or Virus (+) ssRNA). They are single-virus RNA genome which is in the nature of mRNA. They are simple virus.

• Group V: Virus RNA single-negative (or Virus (-) ssRNA). They are RNA viruses with single-polarity antimensajero. They have an RNA-dependent RNA polymerase in a chain. Thus, within the infected cell are complementary to the RNA genome and acts of mRNA.

• Group VI: Virus RNA single-retrotranscrito (or ssRNA virus-RT). They are RNA viruses whose genome could act as a messenger but "in vivo" does not. They have a reverse transcriptase that a genome RNA transcribed from a DNA molecule, first of a string and then two. And subsequently using the cellular enzymes are developing a messenger. These viruses are capable of reaching the nucleus of cells and inserted into the chromosomes of cells that infect: they are retroviruses.

• Group VII: bicatenario retrotranscrito Virus DNA (dsDNA-Virus or RT). It is the most recently discovered and described. It has a genome DNA bicateario which is expressed as a messenger, which translates as group I. However, when the encapsidación, is the messenger that encapsida. This, by retrotranscripción from a reverse transcriptase, inside the virion, a new form of a DNA molecule, the first monkey and then bicatenaria, which turns into the genome of the virus. Are clear examples of these rarities, families and Herpesviridae Caulimoviridae.

Classification of ICTV.
The ICTV (International Committee on Taxonomy of Viruses) tries to get a universal classification that can function as the necessary standard classification of the virus, regulating the formal description of new strains and ordering its location within the scheme Qualifier. tries to the rules of nomenclature and classification resemble as closely as possible to the traditional standard of the classification of organisms using some of its categories, suffixes that indicate the taxonomic status and applying italics to the names of the taxa:

Order (-viral) Family (-viridae) Subfamily (-virinae) Gender (virus) Species (virus)

The names of the senior taxa are written in italics, as in the International Code of Botanical Nomenclature (but not the zoo). The names of species follow a systematic rule, named in the vernacular with the disease name and the word for viruses. For example, the human immunodeficiency virus (HIV). The recognition of orders has been delayed and are used sparingly, having been designated so far only three, so that most of the 80 families have not yet been assigned to none. The list contains about 4,000 species ICTV.

VIRUS

The virus(from the latin word virus that means toxine or poison) are a parasite biologic entity that are basicly formed of nucleic acid and proteins denominated capsid.The virus prolify by absorbing the DNA of some cells and then the cell die s and the virus multiply.

This things are in the frontier of the live and the nonlive things becouse they dont have metebolism becouse of thi the entibiotics have no effect on this entities.

the viral genoma is very small becouse of this tha virus cant codify many proteins. for resolving this problem the capsid is formed of one or few proteins that are formed on a simetric patern is becouse of this that are two tipes of virus:

Helical virus:in this type the proteins of the capsid are formed in a ciindric form like in the tabaco virus.

Spherical virus:in this type of virus the proteins are formed on a polyhedra form.

Another way to classify the virus is according to the type of genetic material they possess, and hence in this category there are only two types of DNA viruses such as bacteriophages which they feed specifically on bacteria, the adenovirus (that causes colds and pink eye disease), the papillomavirus that causes warts. The other category is made up of RNA viruses or retroviruses such as the influenza, hepatitis, the mosaic of snuff and AIDS.

Not all viruses cause the immediate death of the infected cell, some, such as invading animal cells, the latter converted into factories perpetual virus, so that the cell membrane does not break at the exit of the virus but it only has pores.

Retroviruses possess within its capsid a single strand of RNA and an enzyme called reverse transcriptase or reversotranscriptasa. Once the viral genome has been introduced into the cell, the DNA constructs reversotranscriptasa from the original mold of RNA, this new DNA is incorporated into the cell chromosome. It was then carried out the transcript, generating molecules of viral RNA, reverse transcriptase and proteins of the capsid.

The virus causes a range of diseases in all living organisms. The viral diseases include colds or flu, herpes, measles, varieties of smallpox, hepatitis, AIDS and encephalitis.

Viruses are usually very specific for their hosts and even the types of cells in multicellular organisms that infect. Currently it is suggested that some viruses have changed their accommodation, the human immunodeficiency virus (HIV), of Ebola.