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Unique Characteristics of Viruses !
#1
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Today medical field is working day and night to find out complete cure from many deadly diseases like HIV- AIDS, Influenza, Measles, Hepatitis, Polio, Herpes Simplex, Rabies etc., and one common thing in all these diseases is that all are viral disease. Therefore the question comes here is what is so unique in viruses as compared to bacteria and other pathogens. Lets us look into it. What virus means and what are the unique characteristics of viruses which differentiate them from other pathogens.

Virology is the study of structure, metabolism, classification, evolution of the mode of infection of viruses and of the use of host genetic material and cell for reproduction. The knowledge of viruses is today helping many researchers to find out the therapy for such deadly diseases. By definition, viruses are intra cellular obligatory parasites. It means they can survive only if they are in host and they are non- living creatures when found outside of the host cell. They utilize host genetic and cellular material for their own reproduction. The classification of viruses is based on the host type they infect. For example if the host is bacteria, they are known as bacteriophages, and further classified as per the host plant, animal fungus etc. The most complex viruses are bacteriophages. One more type of classification is found in the viruses. It is based on the geometrical shape of the capsid of the virus. The capsid of viruses is either helix or icosahedrons. Also during this type of classification, structure of virus is considered for examples the presence or the absence of lipid envelop differentiate the virus types. Such type of complex structural geometric forms is not found in bacteria or other pathogens. This is one of the unique characteristics of viruses. Another is that they can only survive in their host which is not the case for bacteria. Today the most widely used classification is based on the Nucleic acid structure. Like DNA viruses and RNA viruses.

Viruses are the smallest microorganisms. They are much smaller than bacteria. The size of viruses ranges from 28 nano meter (nm) up to 465 nm. This also means that they are so small that they cannot be seen through light microscopes. This type of small sizes is another unique characteristic of viruses. So if they are so small how their molecular shape and every detail study is done? The use of modern electron microscope helps to completely study viruses. Also many a times X-ray crystallography and spectroscopy is used for the research in the field of virology. Today with the use of such sophisticated instruments, it is known that there are around two thousand species and around three hundred genera of viruses worldwide.

During the course of virology development, many infectious entities which are even smaller than viruses have been identified. These are sub viral particles and can cause diseases in humans and even animals. These are Viroids which is itself a naked circular RNA molecule capable of infecting plants. This is another unique characteristic of viruses and related entities. Such sub viral particle is nucleic acid molecule either with or without capsid is capable of infection with the help of another virus and is capable to reproduce in host. This type of sub viral entity is known as satellite. Prions are the protein which is also capable of creating abnormal health along with the help of other prions.

Today the many important diseases are caused by viruses. Apart from infectious disease, many viruses have been found which are contributing in the development of cancerous cells. These are known as oncoviruses. Such characteristics of viruses make them unique and different from bacteria with respect to shape, size, mode of reproduction, infection, pathogencity. This all create curiosity among scientist and researcher to study them in every details and to develop a successful treatment therapy against them to help patient to survive from such deadly viral diseases. Many of such techniques and methods of their treatment is being successfully applied all over the world. The main such is vaccination against such diseases. As always prevention is better than cure.
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#2
Benefits of viruses

Just like any other species on the Earth, viruses need to fight to survive and to replicate as much as possible. Due to their small size, inability to live without host and high growing potential, they will induce more or less damage in humans, plants or animals - their typical hosts. Although the list of incurable viral diseases is long, they could be more than helpful in various fields of human life. Scientists realized potential of different viruses and today, whole viruses or their particles represent inevitable part of modern medicine, genetic engineering and agriculture.

Viruses in medicine

Long time ago, doctors realized that people can develop immunity against certain diseases when they are partially exposed to the infective agent. That was the beginning of the era of vaccines that helped in saving millions of lives. Besides vaccination against classic viral diseases such as chicken pox, measles, polio and other, new generation of vaccines that could prevent cancer was developed. Some viruses, such as human papillomavirus and hepatitis B virus induce cervical and liver cancers, respectively. Vaccines against these types of viruses are developed and they already proved to be effective. Although modern age is associated with synthetic vaccines (faster and cheaper production and broader application compared to old fashion vaccines), viruses still represent huge and very important component in vaccine production.

Due to fast and easily traceable replication, scientists often use viruses to study pathology of viruses and immune response, DNA or RNA replication, protein production and genetics in general. Ability of viruses to incorporate into host’s genome is widely used in gene therapy. Using viral vectors, corrected versions of the impaired genes (genes that underwent mutation or become silenced for some other reason) can be inserted in the host's tissue. Once incorporated in the host's DNA, virus particle will start expressing protein of interest, one whose absence resulted in disease. Principle of action can be explained on the example of diabetes type I. This is an autoimmune disease: pancreatic beta cells are recognized as foreign bodies and destroyed by immune system. End result - lack of insulin and inability of patient to lower its blood glucose level without insulin therapy for the rest of his/her life. Potential solution for diabetes lays in gene therapy. Viral particle bearing genes that encode insulin should target and incorporate into DNA of the pancreatic cells. When they reach desired tissue, they could turn some of pancreatic cells into beta cells and induce production of insulin, which will automatically decrease (or cease completely) the need for exogenous therapy. Although this method still needs to be improved, it has a great chance of becoming regular therapy for insulin in the future. A lot of other diseases could be treated by gene therapy and researchers are especially focused on the field of cancer. Viruses that are mostly used as vectors in gene therapy are adeno- and retroviruses. Besides them, adeno-like viruses, lenti-, alpha- and pox viruses are also used.

Some viruses live inside bacterial cells. Those are called bacteriophages. One of the latest news associated with bacteriophages is that they could prevent acne formation in people prone to this issue. Acne develops as the result of increased activity of Propionibacterium species. Since these bacteria normally host ~11 types of viruses, acne could be prevented by increasing the number of bacteriophages that destroy bacterial wall to release themselves as soon as they finish replication. When genomes of these viruses were sequenced, it was discovered that they share the same mechanism of infecting bacteria and thus all of them could be useful in production of medicines that could kill acne causing bacteria.

Viruses in agriculture

Viruses are also beneficial in agriculture. They improve qualities of plants and animals by serving as genetic vectors in creation of the transgenic organisms. Other than that, viruses can be used in the pest control. By choosing the right viral agent, certain types of insects can be eliminated from the harvest. Baculoviruses are group of viruses that attack and kill around 600 species of insects. When solution containing baculoviruses are sprayed over the plants, caterpillars will infect themselves with viruses and die after some time. This method is safe for humans because viruses of this group can't infect humans. Besides that, viruses of the surface of the plant will be destroyed via sunlight or high temperature.

These are just some of the examples showing benefits of viruses. Just like other species on the Earth, they need to fight to survive, even though some of their mechanisms are harmful for people. If you consider how many species and beautiful things humans managed to destroy so far, maybe our species is more pathogenic than all viruses together.
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