Various Kind of Human disease Virus

A virus (from the Latin virus meaning toxin or poison) is a sub-microscopic infectious agent that is unable to grow or reproduce outside a host cell. Viruses infect all cellular life. The first known virus, tobacco mosaic virus, was discovered by Martinus Beijerinck in 1898,[1] and now more than 5,000 types of virus have been described.[2] The study of viruses is known as virology, and is a branch of microbiology.

Viruses consist of two or three parts: all viruses have genes made from either DNA or RNA, long molecules that carry genetic information; all have a protein coat that protects these genes; and some have an envelope of fat that surrounds them when they are outside a cell. Viruses vary in shape from simple helical and icosahedral shapes, to more complex structures. They are about 1/100th the size of bacteria.[3] The origins of viruses are unclear: some may have evolved from plasmids—pieces of DNA that can move between cells—others may have evolved from bacteria.

Viruses spread in many ways; plant viruses are often transmitted from plant to plant by insects that feed on sap, such as aphids, while animal viruses can be carried by blood-sucking insects. These disease-bearing organisms are known as vectors. Influenza viruses are spread by coughing and sneezing, and others such as norovirus, are transmitted by the faecal-oral route, when they contaminate hands, food or water. Rotaviruses are often spread by direct contact with infected children. HIV is one of several viruses that are transmitted through sex.

Not all viruses cause disease, as many viruses reproduce without causing any obvious harm to the infected organism. Some viruses such as hepatitis B can cause life-long or chronic infections, and the viruses continue to replicate in the body despite the hosts' defence mechanisms. However, viral infections in animals usually cause an immune response, which can completely eliminate a virus. These immune responses can also be produced by vaccines that give lifelong immunity to a viral infection. Microorganisms such as bacteria also have defences against viral infection, such as restriction modification systems. Antibiotics have no effect on viruses, but antiviral drugs have been developed to treat life-threatening and more minor infections.

From: Wikipedia

0 comments:

Post a Comment

Lyrics buy books online GSM Literature books grameenphone Bangladesh Chord Guitar Linux STRATEGIC ANALYSIS Of GRAMEENPHONE LIMITED Tips love Asia Computer Credit Human Jackson Michael Money Poem Romantic STRATEGIC ANALYSIS Swine Technology Ubuntu Virus Visa card classification diseases friend problem reviews 1976 Ambition Analysis Animal virology Connection Daffodils Definition Depression Earn Fun Funny HIV HRM Practices of Grameenphone Limited Influenza Internet Lifestyle Medical disasters Music Nokia Notes Online Pandemics Phone Photography Professional Revolution Security System Tricks Windows Wordsworth adsense disasters flixya follow friendship genre good google highest standard technology international outbreak pig point pray research transmission 20 2007 2008 2009 AIDS ATM Acronyms Affiliate America Argentina Artcell Boot Butterfly Causes of death Che Command Company Background Currency DARWIN DEVELOPMENT OF ENGLISH ANXIETY SCALE FOR SECONDARY SCHOOL Debit Decision Depression Cure Discovery and invention controversies Disease Domain E-links FM Radio Fidel Castro Flirt Forex Free Genuine Guevara HM Immunodeficiency Indian Industry and Competitive Analysis Japanese Wife John Ruskin Jokes LRB Laptop League Liberation Link Linkin Literary MLM Marxist Movements Nothing ORIGIN OS Opperating Park Post Premier Punch Result Retroviruses Royality SPECIES SSC STUDENTS Scum Sexually transmitted diseases and infections Shania Twain Smile Socialism Song Sports leagues T20 Tale Terms Twenty USA Update Wikipedia Winnings XP airport bestseller broadcast company competitions cpc cricket customer data depressed domestic download dual ebook effective email establishments features flu forum gmail god government habits happy important index james leagues major mask methodology objectives pictures poetry pop prayer read seaport shop online short story slack sports study teens tutorial twilight unijoy