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[Vote] Viruses?!

Apakah virus dapat mati?! [Post ur argument to discuss it]

  • Ya .. Virus Bisa Mati ..

    Suara: 4 22,2%
  • Tidak .. Virus Hanya Dapat Non-Active, Tapi Tidak Mati

    Suara: 14 77,8%

  • Total suara
    18

Th0R

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Belajar pelajaran SMP/SMU di berbagai sekolah di Indonesia, tentu anda sekalian kerapkali membahas yang namanya Virus dan Backteria. Sekarang, sering banget ada tanggapan mengenai Virus. Bagaimana dan Mengapa virus itu sendiri ..

Akan tetapi sewaktu dahulu saya mendirikan ISCF (Indonesian Science Community Forum), masih banyak orang yang salah berasumsi mengenai Virus itu sendiri.

Vote ini hanya untuk menjadi tongkat ukur mengenai pengertian kita mengenai berbagai hal kecil yang sebenernya cukuplah berguna.

Thanks.
Th0R
 
katanya virus bakal mati kalo ud berumur lbi dari 20tahun ...bner ga?
g taunya juga dari komik DDS,jadi maklum kalo salah :D
 
bukankah lebih baik pertanyaannya diubah, jadi apakah virus itu mahluk hidup :D
 
Nope ..
Virus sudah di yakini 100% sebagai NON-LIVING things dan itu jelas sekali ditulis pada berbagai buku yg membahas mengenai hal tersebut, yang kebanyakan adalah buku biologi .. Akan tetapi kenyataan bahwa virus bisa dikatakan "mati" atau tidak masihlah menjadi sebuah tanda tanya besar dikalangan sebagian besar orang ..

So ..
What do u think?!

Thanks.
Th0R
 
lah situ dah jawab pertanyaannya sendiri kan "NON LIVING" berarti virus cm bs dikatakan tdk aktif bukannya mati :P
 
Masih salah bung Alex ..

Next please xD

Thanks.
Th0R
 
kalo non active bknnya udh mati? /hmm
Apa maksud om thor suatu saat mereka bisa active kembali setelah non active?
Coz selama ini wa kira virus n bacteri itu makhluk hidup../swt /heh
 
Backteria adalah mahkluk hidup ..
Sedangkan virus digolongkan sebagai NON-LIVING things ..
Setidaknya itulah yang kebanyakan ditulis pada buku buku tingkat SMP dan SMU di Indonesia dan beberapa negara sekitar. Akan tetapi apabila kita membahasnya secara lebih mendalam, benarkah mereka itu non living things?! Apakah mereka bisa mati (Dalam arti benar benar mati)?? Atau hanya bisa non-active dan bisa active lagi dengan kondisi tertentu??

Akan saya jawab setelah melihat tanggapan teman teman sekalian.

Thanks.
Th0R
 
Masih salah bung Alex ..

Next please xD

Thanks.
Th0R
lolz kan g cm meneruskan yg anda tuliskan kalau virus adalah non living, mungkinkah sesuatu yg bukan merupakan mahluk hidup bisa mati? :D
 
Tergantung darimana digolongkan nya.
Virus disebut sebagai NON Living things, karena apa?! Dan apa yang menyebutkan bisa dikatakan mati dan non-active. Anda tidak dapat memutuskan tanpa mengetahui kriteria dari itu semua kan? xD

Thanks.
Th0R
 
Tergantung darimana digolongkan nya.
Virus disebut sebagai NON Living things, karena apa?! Dan apa yang menyebutkan bisa dikatakan mati dan non-active. Anda tidak dapat memutuskan tanpa mengetahui kriteria dari itu semua kan? xD

Thanks.
Th0R
oleh karena itu saya bertanya, bukankah sebelum mempertanyakan virus itu bs mati atau hanya tidak aktif bukankah sebaiknya diperdebatkan dl virus itu mahluk hidup atau bukan :D

Newer Definitions of Life

Life may (somewhat irreverently) be defined in general terms as:

"The phenomenon associated with the replication of self-coding informational systems",

or more specifically as:

"The phenomenon associated with the replication of nucleic acids".

- Rybicki EP, 1996.



Another more serious view:

"Life can be viewed as a complex set of processes resulting from the actuation of the instructions encoded in nucleic acids. In the nucleic acid of living cells these are actuated all the time; in contrast, in a virus they are actuated only when the viral nucleic acid, upon entering a host cell, causes the synthesis of virus-specific proteins. Viruses are thus "alive when they replicate in cells, while outside cells viral particles are metabolically inert and are no more alive than fragments of DNA."

- Dulbecco R and Ginsberg HS, 1980. Virology, p.854-855 (originally published as a section in Microbiology, 3rd Edn., Davis et al., Harper and Row, Hagerstown).
 
klo menurut gue virus tidak bisa mati tetapi dia bisa d nonaktifkan tetapi ketika ada sesuatu yang merangsang pertumbuhannya dia bisa menjadi aktif kembali /no1
sori klo salah itu menurut gue sih /no1
 
Virus mati pada suhu yg tinggi menurut ahli nya.....

Virus adalah parasit berukuran mikroskopik yang menginfeksi sel organisme biologis. Virus hanya dapat bereproduksi di dalam material hidup dengan menginvasi dan mengendalikan sel makhluk hidup karena virus tidak memiliki perlengkapan selular untuk bereproduksi sendiri. Istilah virus biasanya merujuk pada partikel-partikel yang menginfeksi sel-sel eukariota (organisme multisel dan banyak jenis organisme sel tunggal), sementara istilah bakteriofage atau fage digunakan untuk jenis yang menyerang jenis-jenis sel prokariota (bakteri dan organisme lain yang tidak berinti sel). Biasanya virus mengandung sejumlah kecil asam nukleat (DNA atau RNA, tetapi tidak kombinasi keduanya) yang diselubungi semacam bahan pelindung yang terdiri atas protein, lipid, glikoprotein, atau kombinasi ketiganya. Genom virus menyandi baik protein yang digunakan untuk memuat bahan genetik maupun protein yang dibutuhkan dalam daur hidupnya.

Virus sering diperdebatkan statusnya sebagai makhluk hidup karena ia tidak dapat menjalankan fungsi biologisnya secara bebas. Karena karakteristik khasnya ini virus selalu terasosiasi dengan penyakit tertentu, baik pada manusia (misalnya virus influensa dan HIV), hewan (misalnya virus flu burung), atau tanaman (misalnya virus mosaik tembakau/TMV).


Ukuran, struktur, dan anatomi


Virus merupakan organisme subselular yang, karena ukurannya sangat kecil, hanya dapat dilihat dengan menggunakan mikroskop elektron. Ukurannya lebih kecil daripada bakteri. Karena itu pula, virus tidak dapat disaring dengan penyaring bakteri.

Partikel virus mengandung DNA atau RNA yang dapat berbentuk untai tunggal atau ganda. Bahan genetik kebanyakan virus hewan dan manusia berupa DNA, dan pada virus tumbuhan kebanyakan adalah RNA yang beruntai tunggal. Bahan genetik tersebut diselubungi lapisan protein yang disebut kapsid. Kapsid bisa berbentuk bulat (sferik) atau heliks dan terdiri atas protein yang disandikan oleh genom virus.

Untuk virus berbentuk heliks, protein kapsid (biasanya disebut protein nukleokapsid) terikat langsung dengan genom virus. Misalnya, pada virus campak, setiap protein nukleokapsid terhubung dengan enam basa RNA membentuk heliks sepanjang sekitar 1,3 mikrometer. Komposisi kompleks protein dan asam nukleat ini disebut nukleokapsid. Pada virus campak, nukleokapsid ini diselubungi oleh lapisan lipid yang didapatkan dari sel inang, dan glikoprotein yang disandikan oleh virus melekat pada selubung lipid tersebut. Bagian-bagian ini berfungsi dalam pengikatan pada dan pemasukan ke sel inang pada awal infeksi.

Kapsid virus sferik menyelubungi genom virus secara keseluruhan dan tidak terlalu berikatan dengan asam nukleat seperti virus heliks. Struktur ini bisa bervariasi dari ukuran 20 nanometer hingga 400 nanometer dan terdiri atas protein virus yang tersusun dalam bentuk simetri ikosahedral. Jumlah protein yang dibutuhkan untuk membentuk kapsid virus sferik ditentukan dengan koefisien T, yaitu sekitar 60t protein. Sebagai contoh, virus hepatitis B memiliki angka T=4, butuh 240 protein untuk membentuk kapsid. Seperti virus bentuk heliks, kapsid sebagian jenis virus sferik dapat diselubungi lapisan lipid, namun biasanya protein kapsid sendiri langsung terlibat dalam penginfeksian sel.

Partikel lengkap virus disebut virion. Virion berfungsi sebagai alat transportasi gen, sedangkan komponen selubung dan kapsid bertanggung jawab dalam mekanisme penginfeksian sel inang.

Penyakit manusia akibat virus


Contoh paling umum dari penyakit yang disebabkan oleh virus adalah pilek (yang bisa saja disebabkan oleh satu atau beberapa virus sekaligus), cacar, AIDS (yang disebabkan virus HIV), dan demam herpes (yang disebabkan virus herpes simpleks). Kanker leher rahim juga diduga disebabkan sebagian oleh papilomavirus (yang menyebabkan papiloma, atau kutil), yang memperlihatkan contoh kasus pada manusia yang memperlihatkan hubungan antara kanker dan agen-agen infektan. Juga ada beberapa kontroversi mengenai apakah virus borna, yang sebelumnya diduga sebagai penyebab penyakit saraf pada kuda, juga bertanggung jawab kepada penyakit psikiatris pada manusia.

Potensi virus untuk menyebabkan wabah pada manusia menimbulkan kekhawatiran penggunaan virus sebagai senjata biologis. Kecurigaan meningkat seiring dengan ditemukannya cara penciptaan varian virus baru di laboratorium.

Kekhawatiran juga terjadi terhadap penyebaran kembali virus sejenis cacar, yang telah menyebabkan wabah terbesar dalam sejarah manusia, dan mampu menyebabkan kepunahan suatu bangsa. Beberapa suku bangsa Indian telah punah akibat wabah, terutama penyakit cacar, yang dibawa oleh kolonis Eropa. Meskipun sebenarnya diragukan dalam jumlah pastinya, diyakini kematian telah terjadi dalam jumlah besar. Penyakit ini secara tidak langsung telah membantu dominasi bangsa Eropa di dunia baru Amerika.

Salah satu virus yang dianggap paling berbahaya adalah filovirus. Grup Filovirus terdiri atas Marburg, pertama kali ditemukan tahun 1967 di Marburg, Jerman, dan ebola. Filovirus adalah virus berbentuk panjang seperti cacing, yang dalam jumlah besar tampak seperti sepiring mi. Pada April 2005, virus Marburg menarik perhatian pers dengan terjadinya penyebaran di Angola. Sejak Oktober 2004 hingga 2005, kejadian ini menjadi epidemi terburuk di dalam kehidupan manusia.


Diagnosis di laboratorium

Deteksi, isolasi, hingga analisis suatu virus biasanya melewati proses yang sulit dan mahal. Karena itu, penelitian penyakit akibat virus membutuhkan fasilitas besar dan mahal, termasuk juga peralatan yang mahal dan tenaga ahli dari berbagai bidang, misalnya teknisi, ahli biologi molekular, dan ahli virus. Biasanya proses ini dilakukan oleh lembaga kenegaraan atau dilakukan secara kerjasama dengan bangsa lain melalui lembaga dunia seperti Organisasi Kesehatan Dunia (WHO).


Pencegahan dan pengobatan

Karena biasanya memanipulasi mekanisme sel induknya untuk bereproduksi, virus sangat sulit untuk dibunuh. Metode pengobatan sejauh ini yang dianggap paling efektif adalah vaksinasi, untuk merangsang kekebalan alami tubuh terhadap proses infeksi, dan obat-obatan yang mengatasi gejala akibat infeksi virus.

Penyembuhan penyakit akibat infeksi virus biasanya disalah-antisipasikan dengan penggunaan antibiotik, yang sama sekali tidak mempunyai pengaruh terhadap kehidupan virus. Efek samping penggunaan antibiotik adalah resistansi bakteri terhadap antibiotik. Karena itulah diperlukan pemeriksaan lebih lanjut untuk memastikan apakah suatu penyakit disebabkan oleh bakteri atau virus.

Etimologi

Walaupun virus ditemukan oleh ahli biologi Rusia Dmitry Ivanovsky pada tahun 1892, nama virus baru digunakan kemudian. Nama tersebut berasal dari kata Latin virus yang berarti racun.
 
@magnum
jadi pendapat kamu apa?
sebaiknya sebelum kita perdebatkan virus itu bs mati atau hanya tdk aktif kita debatkan dl virus itu mahluk hidup atau bukan, karena bagaimana caranya suatu mahluk yg tdk hidup bs mati :P nah kalau virus tergolong mahluk hidup br kita lanjutkan debat sesuai topik
 
virus makhluk kecil yg berbentuk micro,dan hanya dapat di lihat dgn microskop elektron

Virus dapat mati,contohnya jika tubuh anda kuat tidka mudah di serang virus

batuk,flu,dll itu di sebabkan karena virus ,entahlah dari mana datang nya karena mereka berbentuks pt parasite....

pernakah anda mendengar pembasmi virus,obat pembasmi virus,dll bahkan virus komputer dapat di basmi.....

Virus dapat mati dgn sendiri nya atau di basmi dgn obat/bahan kimia lainnya...

ada banyak virus yg sudah ada obat yg dpt membasmi nya,

contoh virus yg blom bisa di basmi dgn obat,flu burung,HIV (AIDS),SARS,dll
mungkin orang itu dapat sembuh jika virus nya hilang sendiri atau orang tsb belum terinfeksi secara parah.....

antibody dalam tubuh manusia juga dapat membunuh virus,dan mempunyai daya tahan terhadap virus sehingga virus tdk mudah menyerang manusia
 
virus makhluk kecil yg berbentuk micro,dan hanya dapat di lihat dgn microskop elektron

Virus dapat mati,contohnya jika tubuh anda kuat tidka mudah di serang virus

batuk,flu,dll itu di sebabkan karena virus ,entahlah dari mana datang nya karena mereka berbentuks pt parasite....

pernakah anda mendengar pembasmi virus,obat pembasmi virus,dll bahkan virus komputer dapat di basmi.....

Virus dapat mati dgn sendiri nya atau di basmi dgn obat/bahan kimia lainnya...

ada banyak virus yg sudah ada obat yg dpt membasmi nya,

contoh virus yg blom bisa di basmi dgn obat,flu burung,HIV (AIDS),SARS,dll
mungkin orang itu dapat sembuh jika virus nya hilang sendiri atau orang tsb belum terinfeksi secara parah.....

antibody dalam tubuh manusia juga dapat membunuh virus,dan mempunyai daya tahan terhadap virus sehingga virus tdk mudah menyerang manusia
"makhluk" dengan menyebutkan kata maklhluk berarti anda setuju kalau virus dikategorikan sebagai makhluk, virus memiliki banyak kekurangan untuk bs dikategorikan sebagai makhluk dan satu2nya yg membuat dia bs dikategorikan ke hitungan makhluk hanya karena memiliki nucleic acid dan kemampuan untuk berinteraksi dgn lingkungannya serta kemampuan untuk replikasi
bs tolong sebutkan virus apa dan obat pembasminya apa ? antibodi bukan untuk membunuh virus, antibodi hanya untuk meningkatkan kekebalan tubuh dari virus, bukan membunuh virus, jikalau ada penjelasan antibodi membunuh virus tolong saya minta link dan sourcenya
 
lahh penjelasan bukan dari Link aja,dari otak sendiri.....
maksudnya antibody juga membantu membasmi virus dan meningkatkan kekebalan tubuh sehingga membuat tubuh tdk gampang terserang virus/penyakit....
kalo sakit sedikit ngak di kasih obat kan bisa sembuh dari mana dong???

virus membawa penyakit...

kalo menenami virus apa dan obat nya
spt batuk(gw gak tau virus nya krn gw anak SMP)pembasmi nya berada di dalam obat batuk....
sama seperti flu....

baca post gw yg pertama

Group:
I: dsDNA viruses
II: ssDNA viruses
III: dsRNA viruses
IV: (+)ssRNA viruses
V: (-)ssRNA viruses
VI: ssRNA-RT viruses
VII: dsDNA-RT viruses

A virus (Latin, poison) is a microscopic particle that can infect the cells of a biological organism. At the most basic level viruses consist of genetic material contained within a protective protein shell called a capsid, which distinguishes them from other virus-like particles such as prions and viroids. The study of viruses is known as virology, and those who study viruses are called virologists.

Viruses are similar to obligate intracellular parasites as they lack the means for self-reproduction outside a host cell, but unlike parasites, which are living organisms, viruses are not truly alive. They infect a wide variety of organisms, both eukaryotes (such as animals and plants) and prokaryotes (such as bacteria). A virus that infects bacteria is known as a bacteriophage, which is used mainly in its shortened form phage.

It has been argued extensively whether viruses are living organisms. They are considered non-living by the majority of virologists as they do not meet all the criteria of the generally accepted definition of life. Among other factors, viruses do not possess a cell membrane or metabolise on their own. A definitive answer is still elusive due to the fact that some organisms considered to be living exhibit characteristics of both living and non-living particles, as viruses do. For those that consider viruses living, viruses are an exception to the cell theory proposed by Theodore Schwann, as viruses are not made up of cells.

200px-Herpes_simpex_virus.jpg


Discovery

Viral diseases such as rabies have affected humans for many centuries, but it wasn't until relatively recently that the cause of these diseases was discovered. In the early 18th century, the wife of an English ambassador to Turkey observed the native women inoculating their children against smallpox, who subsequently became immune to the disease. In the late 18th century, Edward Jenner observed and studied a milkmaid who had caught cowpox previously and subsequently became immune to smallpox, a similar virus.

Charles Chamberland developed a porcelain filter in the late 19th century which was used to indirectly study the first documented virus, tobacco mosaic virus. Shortly afterwards, Dmitri Ivanowski published his experiments showing that crushed leaf extracts of infected tobacco plants were still infectious even after filtering any bacteria. At about the same time, several others documented filterable disease-causing agents, with several independent experiments showing that viruses were different to bacteria and caused disease in living organisms.

In the early 20th century, Frederick Twort discovered that even bacteria could be attacked by viruses. Felix d'Herelle, working independently, showed that a preparation of viruses caused areas of cellular death on thin cell cultures spread on agar. Counting these degraded areas allowed him to estimate the original number of viruses in the suspension. Finally, in 1935 Wendell Stanley crystallised the tobacco mosaic virus and found it to be mostly protein, and a short time later the virus was separated into both protein and a nucleic acid parts.


Origins

The origins of modern viruses are not entirely clear, and there may not be a single mechanism of origin that can account for all viruses. As viruses do not fossilise well, molecular techniques have been the most useful means of hypothesising how they arose. Research in microfossil identification and molecular biology may yet discern fossil evidence dating to the Archean or Proterozoic eons. Two main hypotheses currently exist:

* Small viruses with only a few genes may be runaway stretches of nucleic acid originating from the genome of a living organism. Their genetic material could have been derived from transferable genetic elements such as plasmids or transposons, which are prone to moving around, exiting, and entering genomes.

* Viruses with larger genomes, such as poxviruses, may have once been small cells which parasitised larger host cells. Over time, genes not required by their parasitic lifestyle would have been lost in a streamlining process known as retrograde- or reverse-evolution. Both the bacteria Rickettsia and Chlamydia are living cells which, like viruses, can only reproduce inside host cells. They lend credence to this hypothesis, as they are likely to have lost genes which enabled them to survive outside a host cell in favour of their parasitic lifestyle.

Other infectious particles which are even simpler in structure than viruses include viroids, satellites, and prions.


Classification


T4bacteriophage.jpg

T4bacteriophage.

In taxonomy, the classification of viruses has proved to be rather difficult due to the lack of fossil record and dispute over whether they are living or non-living. They do not fit easily into any of the domains of biological classification and therefore classification begins at the family rank. However, the domain name of Acytota has been suggested. This would place viruses on a par with the other domains of Eubacteria, Archaea, and Eukarya. Not all families are currently classified into orders, nor all genera classified into families.

As an example of viral classification, the chicken pox virus belongs to family Herpesviridae, subfamily Alphaherpesvirinae and genus Varicellovirus. It remains unranked in terms of order. The general structure is as follows.


Kode:
  Order (-virales)

        Family (-viridae)

            Subfamily (-virinae)

                Genus (-virus)

                    Species (-virus)
The International Committee on Taxonomy of Viruses (ICTV) developed the current classification system and put in place guidelines that put a greater weighting on certain virus properties in order to maintain family uniformity. In determining order, taxonomists should consider the type of nucleic acid present, whether the nucleic acid is single- or double-stranded, and the presence or absence of an envelope. After these three main properties, other characteristics can be considered: the type of host, the capsid shape, immunological properties and the type of disease it causes.

In addition to this classification system, the Nobel Prize-winning biologist David Baltimore devised the Baltimore classification system. This places a virus into one of seven Groups, which separate viruses based on their mode of replication and genome type. The ICTV classification system is used in conjunction with the Baltimore classification system in modern virus classification.


Structure


A complete virus particle, known as a virion, is little more than a gene transporter, consisting at the most basic level of nucleic acid surrounded by a protective coat of protein called a capsid. A capsid is composed of proteins encoded by the viral genome and its shape serves as the basis for morphological distinction. Virally coded protein units called protomers will self-assemble to form the capsid, requiring no input from the virus genome - however, a few viruses code for proteins which assist the construction of their capsid. Proteins associated with nucleic acid are more technically known as nucleoproteins, and the association of viral capsid proteins with viral nucleic acid is called a nucleocapsid.

In general, four main morphological virus types can be identified:


Helical Viruses

5e95bd23.png

Diagram of a helical capsid
Enlarge
Diagram of a helical capsid
Helical capsids are composed of a single type of protomer stacked around a central circumference to form an enclosed tube resembling a spiral staircase. This arrangement results in rod-shaped virions which can be short and rigid, or long and flexible. Long helical particles must be flexible in order to prevent forces snapping the structure. The genetic material is housed on the inside of the tube, protected from the outside. Overall, the length of a helical capsid is related to the length of the nucleic acid contained within it, while the diameter is dependent on the overall length and arrangement of protomers. The well-studied tobacco mosaic virus is a helical virus.


Icosahedral Viruses

c3b7dc6b.jpg

Icosahedral capsid symmetry results in a spherical appearance of viruses at low magnification but actually consists of capsomers arranged in a regular geometrical pattern, similar to a soccer ball, hence they are not truly "spherical". Capsomers are ring shaped structures constructed from five to six copies of protomers. These associate via non-covalent bonding to enclose the viral nucleic acid, though generally less intimately than helical capsids, and may involve one type of protomer or more.

Icosahedral architecture was employed by R. Buckminster-Fuller in his geodesic dome, and is the most efficient way of creating an enclosed robust structure from multiple copies of a single protein. The number of proteins required to form a spherical virus capsid is denoted by the T-number, where 60×t proteins are necessary. In the case of the hepatitis B virus the T-number is 4, therefore 240 proteins assemble to form the capsid.


Enveloped viruses
5f0babda.png

In addition to a capsid some viruses are able to hijack a modified form of the cell membrane surrounding an infected host cell, thus gaining an outer lipid layer known as a viral envelope. This extra membrane is studded with proteins coded for by the viral genome and host genome, however the lipid membrane itself and any carbohydrates present are entirely host-coded.

The viral envelope can give a virion a few distinct advantages over other "naked" virions, such as protection from enzymes and chemicals. The proteins studded upon it can include glycoproteins functioning as receptor molecules, allowing healthy cells to recognise virions as "friendly" and resulting in the possible uptake of the virion into the cell. Some viruses, however, are so dependent upon their viral envelope that they fail to function if it is removed.


Complex Viruses

c7fc7cf3.png

These viruses possess a capsid which is neither purely helical, nor purely icosahedral, and which may possess extra structures such as protein tails or a complex outer wall. Some bacteriophages have a complex structure consisting of an icosahedral head bound to a helical tail, the latter of which may have a hexagonal base plate with many protruding protein tail fibres.

The poxviruses are large, complex viruses which possess unusual morphology. The viral genome is associated with proteins within a central disk structure known as a nucleoid. The nucleoid is surrounded by a membrane and two lateral bodies of unknown function. Covering the virus is an outer envelope with a thick layer of protein studded on its surface. The whole particle is slightly pleiomorphic, ranging from ovoid to brick shape.



Size

The majority of viruses which have been studied have a capsid diameter between 10 and 300 nanometres. To put viral size into perspective, a medium sized virion next to a flea is roughly equivalent to a human next to a mountain twice the size of Mount Everest. Some filoviruses have a total length that can reach up to 1400 nm, however their capsid diametres are only about 80 nm. While most viruses are unable to be seen with a light microscope, some are larger than the smallest bacteria and can be seen under high magification. Both scanning and transmission electron microscopes are commonly employed to visualise virus particles.

A notable exception to the normal viral size range is the recently discovered mimivirus, with a diameter of 400 nm. They also hold the record for the largest viral genome size, possessing about 1000 genes (some bacteria only possess 400) on a genome approximately 1.2 megabases in length. Their large genome also contains many genes which are conserved in both prokaryotic and eukaryotic genes. The discovery of the virus has led many scientists to reconsider the controversial boundary between living organisms and viruses,which are currently considered as mere mobile genetic elements.


Genetic material

Both DNA and RNA are found in viral species, but generally a species will have either one or the other—not both. One exception is the human cytomegalovirus, which contains both a DNA core and mRNA. The nucleic acid can be either single-stranded or double-stranded, depending on the species. Therefore viruses as a group contain all four possible types of nucleic acids: double-stranded DNA, single-stranded DNA, double-stranded RNA and single-stranded RNA. Animal virus species have been observed to possess all combinations, whereas plant viruses tend to have single-stranded RNA. Bacteriophages tend to have double-stranded DNA. Also, the nucleic acids can be either linear or a closed loop.


Genome size in terms of the weight of nucleotides varies quite substantially between species. The smallest genomes code for only four proteins and weigh about 10(6) daltons, while the largest weigh about 10(8) daltons and code for over one hundred proteins. Some virus species possess abnormal nucleotides, such as hydroxymethylcytosine instead of cytosine, as a normal part of their genome.

For viruses with RNA as their nucleic acid, the strands are said to be either positive-sense (also called plus-strand) or negative-sense (also called minus-strand) depending on whether it is complementary to viral mRNA. Positive-sense viral RNA is identical to viral mRNA and thus can be immediately translated by the host cell. Negative-sense viral RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an RNA polymerase before translation.

All double-stranded RNA genomes and some single-stranded RNA genomes are said to be segmented, or divided into separate parts. Each segment may code for one protein, and they are usually found together in one capsid. Not all segments are required to be in the same virion for the overall virus to be infectious, as can be seen in the brome mosaic virus.



Viruses and disease

Examples of common human diseases caused by viruses include the common cold, the flu, chickenpox and cold sores. Serious diseases such as Ebola, AIDS, bird flu and SARS are all also caused by viruses. The relative ability of viruses to cause disease is described in terms of virulence. Other diseases are under investigation as to whether they too have a virus as the causative agent, such as the possible connection between Human Herpesvirus Six (HHV6) and neurological diseases such as multiple sclerosis and chronic fatigue syndrome. Recently it was also shown that cervical cancer is partially caused by papillomavirus, representing evidence in humans of a link existing between cancer and an infective agent. There is current controversy over whether the borna virus, previously thought of as causing neurological disease in horses, could be responsible for psychiatric illness in humans.

Viruses have many different mechanisms by which they produce disease in an organism, which largely depends on the species. Mechanisms at the cellular level primarily include cell lysis, the breaking open and subsequent death of the cell. In multicellular organisms, if enough cells die the whole organism will start to suffer the carry-on effects. Although many viruses result in the disruption of healthy homeostasis, resulting in disease, they may reside relatively harmlessly within an organism. An example would include the ability of the herpes simplex virus, which cause coldsores, to remain in a dormant state within the human body.



Epidemics



A number of highly lethal viral pathogens are members of the Filoviridae. Filoviruses are filament-like viruses that cause viral hemorrhagic fever, and include the Ebola and Marburg viruses. The Marburg virus attracted widespread press attention in April 2005 for an outbreak in Angola. Beginning in October 2004 and continuing into 2005, the outbreak was the world's worst epidemic of any kind of viral hemorrhagic fever.

Native American populations were devastated by contagious diseases, particularly smallpox, brought to the Americas by European colonists. It is unclear how many Native Americans were killed by foreign diseases after the arrival of Columbus in the Americas, but the numbers have been estimated to be close to 70% of the indigenous population. The damage done by this disease may have significantly aided European attempts to displace or conquer the native population.

Detection, purification and diagnosis

In the laboratory, several techniques for growing and detecting viruses exist. Purification of viral particles can be achieved using differential centrifugation, isopycnic centrifugation, precipitation with ammonium sulphate or ethylene glycol, and removal of cell components from a homogenised cell mixture using organic solvents or enzymes to leave the virus particles in solution.

Assays to detect and quantify viruses include:.


* Hemagglutination assays, which quantitatively measure how many virus particles are in a solution of red blood cells by the amount of agglutination the viruses cause between them. This occurs as many viruses are able to bind to the surface of one or more red blood cells.
* Direct counts using an electron microscope. A dilute mixture of virus particles and beads of known size are sprayed onto a special sheet and examined under high magnification. The virions are counted and the number extrapolated to estimate the number of virions in the undiluted mixture.
* Plaque assays involve growing a thin layer of host cells onto a culture dish and adding a dilute mixture of virions onto it. The virions will infect and kill the cells they land on, producing holes in the cell layer known as plaques. The number of plaques can be counted and the number of virions estimated from it.


Detection and subsequent isolation of new viruses from patients is a specialised laboratory subject. Normally it requires the use of large facilities, expensive equipment, and trained specialists such as technicians, molecular biologists, and virologists. Often, this effort is undertaken by state and national governments and shared internationally through organizations like the World Health Organization.

Prevention and treatment


Because viruses use the machinery of a host cell to reproduce and also reside within them, they are difficult to eliminate without killing the host cell. The most effective medical approaches to viral diseases so far are vaccinations to provide resistance to infection, and drugs which treat the symptoms of viral infections. Patients often ask for, and physicians often prescribe, antibiotics. These are useless against viruses, and their misuse against viral infections is one of the causes of antibiotic resistance in bacteria. However, in life-threatening situations the prudent course of action is to begin a course of antibiotic treatment while waiting for test results to determine whether the patient's symptoms are caused by a virus or a bacterial infection.

Etymology

The word is from the Latin virus referring to poison and other noxious things, first used in English in 1392. Virulent, from Latin virulentus "poisonous" dates to 1400. A meaning of "agent that causes infectious disease" is first recorded in 1728, before the discovery of viruses by the Russian-Ukrainian biologist Dmitry Ivanovsky in 1892. The adjective viral dates to 1948. Today, Virus is used to describe the biological viruses discussed above and also as a metaphor for other parasitically-reproducing things, such as memes or computer viruses (since 1972). The neologism virion or viron is used to refer to a single infective viral particle.

The Latin word is from a Proto-Indo-European root *weis- "to melt away, to flow," used of foul or malodorous fluids. It is a cognate of Sanskrit viṣam "poison,", Avestan viš- "poison," Greek ios "poison," Old Church Slavonic višnja "cherry," Old Irish fi "poison," Welsh gwy "fluid"; Latin viscum (see viscous) "sticky substance" is also from the same root.

The English plural form of virus is viruses. No reputable dictionary gives any other form, including such "reconstructed" Latin plural forms as viri (which actually means men), and no plural form appears in the Latin corpus (See plural of virus). The word does not have a traditional Latin plural because its original sense, poison is a mass noun like the English word furniture, and, as pointed out above, English use of virus to denote the agent of a disease predates the discovery that these agents are microscopic parasites and thus in principle countable. Naturally this point can, and will, be extensively argued.
 
karena ini secara ilmiah makanya perlu bukti yg otentik donq beda dgn filsafat......
baca quote dr post kamu ini mas
Because viruses use the machinery of a host cell to reproduce and also reside within them, they are difficult to eliminate without killing the host cell. The most effective medical approaches to viral diseases so far are vaccinations to provide resistance to infection, and drugs which treat the symptoms of viral infections. Patients often ask for, and physicians often prescribe, antibiotics. These are useless against viruses, and their misuse against viral infections is one of the causes of antibiotic resistance in bacteria. However, in life-threatening situations the prudent course of action is to begin a course of antibiotic treatment while waiting for test results to determine whether the patient's symptoms are caused by a virus or a bacterial infection.
sepertinya berlawanan dengan statement kamu
 
IMHO virus tidak dapat mati, hanya dapat non-aktif.

seperti halnya sakit cacar air, apabila anda telah sambuh, virus dari cacar air itu sendiri tidak hilang/mati, namun dia berubah sifat yang dimana menjadi preventif (seperti immune)

makanya orang hanya dapat sakit cacar air sekali saja seumur hidupnya.
 
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