Viruses are mainly classified according to the type and structure of their genome and their replication process, not because of the diseases they cause. Thus, there are DNA viruses and RNA viruses; Both types can have single or double strands of genetic material. Single-stranded RNA viruses are still in those with (+) – divided Sense RNA – sense and those with (-). DNA viruses typically replicate in the nucleus of the host cell and RNA viruses typically replicate in the cytoplasm. , Sense RNA viruses called retroviruses a different Replication method – however certain single strand use – (+).

Viruses are the smallest parasites, typically in the range of 0.02 to 0.3 microns, although recently more very large viruses which are up to 1 microns long (Mega virus Pandora virus) have been discovered. Viruses depend for their propagation down completely of cells (bacterial, plant or animal). Viruses have an outer cover of protein and sometimes lipid, an RNA or DNA core and sometimes enzymes that are essential for the first steps of viral replication. Viruses are mainly classified according to the type and structure of their genome and their replication process, not because of the diseases they cause. Thus, there are DNA viruses and RNA viruses; Both types can have single or double strands of genetic material. Single-stranded RNA viruses are still in those with (+) – divided Sense RNA – sense and those with (-). DNA viruses typically replicate in the nucleus of the host cell and RNA viruses typically replicate in the cytoplasm. , Sense RNA viruses called retroviruses a different Replication method – however certain single strand use – (+). Retroviruses utilize reverse transcription to (a provirus) of their RNA genome to create a double-stranded DNA copy which is inserted in the genome of the host cell. Reverse transcription is carried out using the enzyme reverse transcriptase, which carries the virus in its shell with him. Examples of retroviruses are human immunodeficiency virus and the human T-cell leukemia viruses. Once the provirus is integrated into the DNA of the host cell, it is transcribed using typical cellular mechanisms to produce viral proteins and genetic material. When the infected cell belongs to the germ line, the integrated provirus can be established as an endogenous retrovirus that is transmitted to offspring. The sequencing of the human genome showed that at least 1% of the human genome consists of endogenous retroviral sequences, indicating past encounters with retroviruses in the course of human evolution. Some endogenous human retroviruses remain transcriptionally active and produce functional proteins (eg. As the Syncytine that contribute to the structure of the human placenta). Some experts speculate that some diseases with unknown aetiology such as multiple sclerosis, certain autoimmune diseases and various cancers might be caused by endogenous retroviruses. Because the RNA transcription does not include the same error checking mechanisms such as DNA transcription, tend RNA viruses, in particular retroviruses, particularly mutations. So that there is an infection, the virus first must adhere to one or attach one of several receptor molecules on the surface of the host cell. Then, the viral DNA or RNA enters the host cell and separates from the outer shell ( “uncoating”) and replicates within the host cell in a process that occurs with the participation of specific enzymes. The newly synthesized viral components then build up to a complete virus particle. Often, the host cell dies and releases new virus, which in turn infect other host cells. Each step of the viral replication comprising other enzymes, and substrates and provides a way to interfere with the infection process. The consequences of viral infection are very different. Many infections cause acute disease after a short incubation period, but some are asymptomatic or cause only mild symptoms that may or may not be recognized only in retrospect. Many viral infections are completely eliminated by the body’s defenses, but some remain in a latent state, and some cause chronic diseases. In a latent infection, viral RNA or DNA remains in host cells, but does not replicate and cause a long time not a disease, sometimes over many years. A latent viral infections may be transferable during the asymptomatic period, which facilitates the spread from person to person. Sometimes a trigger (especially immunosuppression) causes reactivation. Viruses that remain latent, include herpes viruses, HIV and papovavirus. Chronic viral infections are characterized by continuous, long-lasting virus excretion; Examples are the congenital infection with the rubella virus or cytomegalovirus and persistent hepatitis B or C, HIV can cause both latent and chronic infections. Some diseases are caused by viral reactivation in the CNS after a very long latency period. These include progressive multifocal leukoencephalopathy (due to the JC virus, a polyomavirus) SSPE (due to the measles virus) and progressive rubella panencephalitis (by rubella). The variant Creutzfeldt-Jakob disease and BSE have been previously called slow viral diseases because they have longer incubations (years). Meanwhile, however, is known to be caused by prions; Prions are proteinaceous pathogens that are not bacterial, fungal or viral conditions and do not contain genetic material (overview of prion diseases). Several hundred different viruses can infect humans. Viruses that primarily infect humans, often spread via respiratory secretions and enteric excretions. Some are sexually and by blood transfer (eg., Via transfusion, contact with mucous membranes or puncture with a contaminated needle) or by tissue transplantation transferred. Many viruses are transmitted by rodent or Arthropodvektoren and bats have been identified as carriers for almost all mammalian viruses recently, including some that are responsible for certain serious human infections (eg. As severe acute respiratory syndrome [SARS]). Viruses occur worldwide, its spread, however, previously influenced by innate resistance undergone infections or previous vaccinations, sanitary hygiene and other measures of public health service and the prophylactic administration of antiviral drugs. The life cycle of zoonotic viruses (arboviruses, arenaviruses and filoviruses) plays mainly in animals from; People are secondary or accidental hosts. These viruses are limited to areas and environments that are able to ensure their non-human infection cycle (vertebrates, arthropods or both). Viruses and tumors Some viruses are oncogenic and predispose to certain malignant tumors: Papillomavirus: Cervical, penile, vaginal, anal, oropharyngeal and oesophageal carcinoma Infection with the human T-cell lymphotropic virus 1: Specific types of human leukemia and lymphoma. Epstein-Barr virus: nasopharyngeal carcinoma, Burkitt’s lymphoma, Hodgkin’s lymphoma and lymphomas in immunosuppressed recipients of transplanted organs. Hepatitis B and C viruses: Hepatocellular carcinomas. Human herpesvirus 8: Kaposi’s sarcoma, the primary effusion lymphoma of serous cavities (BCBL = Body Cavity-Based Lymphoma) and Castleman’s disease (a lymphoproliferative disease). Diagnosis Some virus-related diseases can be diagnosed clinically or epidemiologically (z. B. well-known viral syndromes such as measles, rubella, Dreitagefieber or roseola infantum, erythema infectiosum and chickenpox) or epidemiologically (eg., During epidemic outbreaks such. B. influenza, norovirus infection and mumps). A definitive laboratory diagnosis is particularly necessary if a specific therapy can be helpful or if the pathogen poses a threat to public health (eg. As pandemic influenza, HIV). Virological laboratories at hospitals can usually test for some viruses go, but for less common diseases (eg. As rabies, eastern equine encephalitis, human parvovirus B19), the samples must be sent to national reference laboratories. (. Editor’s note: B. Friedrich Löffler Institute for Robert Koch Institute) Serological studies during the acute and convalescent stage are sensitive and specific, but slowly; the diagnosis can sometimes be accelerated by virus culture, PCR or virus antigen detection. Occasionally, a histopathology with electron microscopy (not light microscopy) can help. For specific diagnostic methods, laboratory diagnosis of infectious diseases. Viral genomes are small; the genome of RNA viruses is in the range of 3.5 kilobases (some retroviruses) to 27 kilobases (some reoviruses) and the genome of DNA virus is in the range of 5 kilobases (some parvoviruses) to 280 kilobases (some poxviruses). This manageable size along with the latest advances in nucleotide sequence analysis technology mean that the partial and complete sequencing of viral genomes will become an integral part of epidemiological investigations of disease outbreaks. Therapy Antiviral drugs The use of antiviral substances making rapid progress. Antiviral Chemotherapy can target the various phases of viral replication. It can interfere with the adhesion of viral particles to host cell membranes or the “uncoating” viral nucleic acids that inhibit cellular receptors or factors that are necessary for viral replication, or specific virus encoded enzymes and proteins, which are produced in the host cell block and that for viral replication, are required for normal host cell metabolism, however. Antiviral drugs are most often therapeutically or prophylactically against herpes viruses (including cytomegalovirus -. Herpes viruses), respiratory viruses (respiratory virus) and HIV (human immunodeficiency virus (HIV)) applied. However, some substances are effective against many different types of virus. Some effective against HIV substances in other viral infections such. B. Hepatitis B verwendet.Interferone Interferons are substances that are released from infected host cells in response to viral or other foreign antigens. There are many different interferons, which have numerous effects such. B. blockage of the translation and transcription of viral RNA and termination of viral replication without interfering with physiological cell functions. Interferons are sometimes coupled to polyethylene glycol (pegylated form) was added, resulting in a slow and sustained release of interferon allowed. Among the viral disorders that are treated with interferon therapy, or have been, including chronic hepatitis B and C, condylomata acuminata Kaposi’s sarcoma The side effects of pro-inflammatory acting interferons include fever, chills, weakness, and myalgia, starting typically 7-12 hours after the first injection and up to 12 hours lasting. may lead to depression and hepatitis as well, at high doses also result in bone marrow suppression. Prevention vaccine vaccine (Overview of immunization) are based on the induction or stimulation of natural, specific immunity. Among the viral vaccines, which are commonly used include hepatitis A, hepatitis B, human papilloma virus, influenza, measles, mumps, polio, rabies, rotavirus, rubella, varicella, yellow fever. Vaccines against adenoviruses and smallpox are available, but only in high-risk groups (eg military. B. recruits) are applied. Viral diseases can be eradicated by good vaccines. Smallpox were eradicated in 1978 and rinderpest (by a virus that is closely related to the human measles virus that causes) was eradicated in the 2011th Polio has been eradicated in almost all countries; in some countries hamper logistics and religious feelings continue vaccination. Measles have been eradicated in some parts of the world, especially in the Americas, but because Measles is highly contagious and vaccination coverage, even in regions where it is considered eradicated, is incomplete, there is a final extinction before not immediate. The prospects for the elimination of other more stubborn virus infections (such as HIV) are currently ungewiss.Immunglobuline immunoglobulins (passive immunization) are available for passive immunization in certain situations. They can be used präexpositionell (z. B. in hepatitis A), postexpositionell (z. B. with rabies or hepatitis) and for treating diseases (eg. As eczema vaccinatum) .Schutzmaßnahmen Many viral infections can (through reasonable protective measures depending are prevented by the transmission of a particular drug). Key measures include hand washing, proper food preparation and water treatment, avoiding contact with sick people and safe sex practices. In infections where insects serve as a vector (eg. As mosquitoes, ticks), avoidance or defense of these vectors is important.

Health Life Media Team

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