*TYPES* –>
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*FORMER VIRUSES*
(viri?)
*SMALLPOX*
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*a virus is a ‘small infectious agent’ that replicates only inside the ‘living cells’ of other ‘organisms’*
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(‘viruses’ can infect all types of life forms, from animals and plants to microorganisms, including ‘bacteria’ and ‘archaea’)
(since dmitri ivanovsky’s 1892 article describing a ‘non-bacterial pathogen’ infecting ‘tobacco plants’, and the discovery of the ‘tobacco mosaic virus’ by ‘martinus beijerinck’ in 1898, about 5,000 virus species have been described in detail, although there are millions of types)
(‘viruses’ are found in almost every ecosystem on ‘earth’ and are the most abundant type of ‘biological entity’)
(the study of ‘viruses’ is known as ‘virology’, a sub-speciality of ‘microbiology’)
(while not inside an infected cell or in the process of infecting a ‘cell’, ‘viruses’ exist in the form of ‘independent particles’)
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(these viral particles, also known as virions, consist of 2 (or 3) parts…)
(i) the genetic material made from either DNA or RNA, long molecules that carry genetic information;
(ii) a protein coat, called the ‘capsid’, which surrounds and protects the genetic material;
and in some cases (iii) an envelope of lipids that surrounds the protein coat when they are outside a cell)
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(the shapes of these virus particles range from simple ‘helical’ and ‘icosahedral’ forms for some virus species to more complex structures for others)
(most virus species have ‘virions’ that are too small to be seen with an optical microscope)
(the average ‘virion’ is about one one-hundredth the size of the average ‘bacterium’)
(the origins of viruses in the evolutionary history of life are unclear: some may have evolved from ‘plasmids’—pieces of DNA that can move between cells—while others may have evolved from ‘bacteria’)
(in ‘evolution’, viruses are an important means of ‘horizontal gene transfer’, which increases genetic diversity)
(‘viruses’ are considered by some to be a ‘life form’, because they ‘carry genetic material’, ‘reproduce’, and ‘evolve’ through ‘natural selection’)
(however they lack key characteristics (such as ‘cell structure’) that are generally considered necessary to count as ‘life’)
(because they possess some but not all such qualities, ‘viruses’ have been described as “organisms at the edge of life”, and as ‘replicators’)
(‘viruses’ spread in many ways)
(viruses in ‘plants’ are often transmitted from plant to plant by ‘insects’ that feed on ‘plant sap’ (such as ‘aphids’))
(viruses in ‘animals’ can be carried by ‘blood-sucking insects’)
(these ‘disease-bearing organisms’ are known as ‘vectors’)
(‘influenza’ viruses are spread by ‘coughing’ and ‘sneezing’)
(‘norovirus’ and ‘rotavirus’ (common causes of ‘viral gastroenteritis’) are transmitted by the ‘faecal–oral route’ and are passed from ‘person’ to ‘person’ by ‘contact’, entering the body in ‘food’ or ‘water’)
(‘HIV’ is one of several viruses transmitted through ‘sexual contact’ and by exposure to ‘infected blood’)
(the range of ‘host cells’ that a ‘virus’ can ‘infect’ is called its “host range”)
(this can be ‘narrow’)
(meaning the virus is capable of infecting ‘few species’)
(…or they can be ‘broad’)
(meaning the virus is capable of infecting ‘many species’)
(‘viral infections’ in animals provoke an ‘immune response’ that usually eliminates the ‘infecting virus’)
(‘immune responses’ can also be produced by ‘vaccines’, which confer an ‘artificially acquired immunity’ to the specific ‘viral infection’)
(however, some ‘viruses’ (including those that cause ‘AIDS’ and ‘viral hepatitis’) evade these ‘immune responses’ and result in ‘chronic infections’)
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(‘anti-biotics’ have no effect on ‘viruses’, but several ‘anti-viral drugs’ have been developed)
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👈👈👈☜*“INFECTIOUS DISEASES”* ☞ 👉👉👉
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💕💝💖💓🖤💙🖤💙🖤💙🖤❤️💚💛🧡❣️💞💔💘❣️🧡💛💚❤️🖤💜🖤💙🖤💙🖤💗💖💝💘
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*🌈✨ *TABLE OF CONTENTS* ✨🌷*
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🔥🔥🔥🔥🔥🔥*we won the war* 🔥🔥🔥🔥🔥🔥