Introduction
Viruses have several characteristics: they are small, have DNA or RNA genomes, and are obligate intracellular parasites. The Virus capsid capabilities to safeguard the nucleic acid from the climate, and some viruses encompass their capsid with a film envelope. Most viruses have icosahedral or helical capsid structure, albeit a couple have complex virion engineering. An icosahedron is a mathematical shape with 20 sides, each made out of a symmetrical triangle, and icosahedral viruses increment the quantity of underlying units in each face to extend capsid size. The classification of viruses is extremely helpful, and the Global Board of trustees on Scientific classification of viruses is the authority body that characterizes infections into order, family, genus, and species taxa.There are as of now seven orders of viruses.
Common Characteristics
Viruses share a few common characteristics
1. They are small in Size.
The littlest of viruses are around 20 nm in breadth, despite the fact that flu and the human immunodeficiency virus have a more ordinary size, around 100 nm in width. Normal human cells are 10-30 μm (microns) in distance across, and that implies that they are for the most part 100 to multiple times bigger than the viruses that are contaminating them.
Notwithstanding, some viruses are altogether bigger than 100 nm. Poxviruses, like the variola virus that causes smallpox, can move toward 400 nm long, and filoviruses, like the hazardous Ebola virus and Marburg virus, are just 80 nm in distance across however stretch out into long strings that can arrive at lengths of more than 1000 nm. A few extremely enormous viruses that contaminate one-celled critters have as of late been found: megavirus is 400 nm in measurement, and pandoraviruses have a circular or ovoid design moving toward 1000 nm long. It is a typical slip-up to feel that all viruses are more modest than microorganisms; most microbes are normally 2000-3000 nm in size, yet certain kinds of microscopic organisms called Mycobacteria can be multiple times less than this, placing them in the scope of these huge viruses. So characteristics of viruses is that they are small in size, this reaches from a couple of nanometers to bigger than certain microorganisms
2.They are obligate intracellular parasites, implying that they are totally subject to the internal environment of the cell to make new infectious virus particles, or virions.
All viruses connect with and tie the outer layer of a cell to acquire passage into the cell. The virus dismantles and its hereditary material (made of nucleic acid) encodes the directions for the proteins that will precipitously collect into the new virions. This is known as de novo replication, from the Latin for “from new." rather than cells, which fill in size and separation similarly in two to imitate, viruses utilize the cell's energy and apparatus to make and gather new virions piece by piece, totally without any preparation.
3. The hereditary material of viruses can be made out of DNA or RNA.
Every single living cell, whether human, creature, plant, or bacterial, have double-stranded DNA(dsDNA) as their hereditary material. Viruses, then again, have genomes, or hereditary material, that can be made out of DNA or RNA (yet not both). Genomes are not really double-stranded, either; unique virus types can likewise have single-stranded DNA (ssDNA) genomes, and viruses with RNA genomes can be ssingle-stranded or double-stranded. A specific virus will just have one kind of nucleic acid genome, nonetheless, thus viruses are not experienced that have both ssDNA and ssRNA genomes, for instance.
Structure
The infectious virus molecule should be let out of the host cell to taint different cells and people. Whether dsDNA, ssDNA, dsRNA, or ssRNA, the nucleic acid genome of the infection should be safeguarded all the while. In the extracellular environment, the virus will be presented to chemicals that could separate or corrupt nucleic acid. Actual burdens, like the progression of air or fluid, could likewise shear the nucleic acid strands into pieces. What's more, popular genomes are helpless to harm by bright radiation or radioactivity, much similarly that our DNA is. On the off chance that the nucleic acid genome of the virus is harmed, creating descendants virions will not be able.
Classification
Viruses are classified based on morphology, chemical composition, and method of replication. The viruses that infect human are at present gathered into 21 families, reflecting just a little piece of the range of the huge number of various viruses whose host goes stretch out from vertebrates to protozoa and from plants and growths to bacteria.
Morphology: viruses are gathered based on size and shape, chemical composition and structure of the genome, and method of replication. Helical morphology is seen in nucleocapsids of numerous filamentous and pleomorphic viruses. Helical nucleocapsids comprise of a helical cluster of capsid proteins (protomers) folded over a helical fiber of nucleic acid. Icosahedral morphology is normal for the nucleocapsids of many "spherical" viruses. The number and arrangement of the capsomeres (morphologic subunits of the icosahedron) are significant in ID and arrangement.. Numerous viruses likewise have an outer envelope.
Chemical Composition and Method of Replication: The genome of an infection might comprise of DNA or RNA, which might be single stranded (ss) or double stranded (ds), linear or circular. . The entire genome might possess possibly one nucleic acid atom (monopartite genome) or a few nucleic acid fragments (multipartite genome). The various sorts of genome require different replication methodologies
Classification of it based on the mode of transmission
Viruses can be classified based on various criteria, including their mode of transmission. The mode of transmission of a virus refers to how the virus spreads from one host to another. Here are some common modes of transmission of viruses and examples of viruses that spread through each mode:
•Contact Transmission: This mode of transmission occurs when a virus spreads through physical contact with an infected person or object. Examples of viruses that spread through contact transmission include herpes simplex virus, human papillomavirus (HPV), and hepatitis B virus.
•Airborne Transmission: This mode of transmission occurs when a virus spreads through the air, usually through coughing or sneezing. Examples of viruses that spread through airborne transmission include influenza virus, SARS-CoV-2 (the virus that causes COVID-19), and measles virus.
•Waterborne Transmission: This mode of transmission occurs when a virus spreads through contaminated water. Examples of viruses that spread through waterborne transmission include hepatitis A virus and norovirus.
•Foodborne Transmission: This mode of transmission occurs when a virus spreads through contaminated food. Examples of viruses that spread through foodborne transmission include hepatitis A virus and norovirus.
•Vector-borne Transmission: This mode of transmission occurs when a virus spreads through a vector, such as a mosquito or tick. Examples of viruses that spread through vector-borne transmission include Zika virus, West Nile virus, and dengue virus.
It is important to note that some viruses can spread through multiple modes of transmission, and the mode of transmission can also depend on various factors, such as the virus's stability, environmental conditions, and the host's immune status.
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