COVID-19,CORONA VIRUS
When we think of the major threats to our national security,the first to come to mind are nuclear proliferation,rouge states and global terrorism.But another kind of threat lurks beyond our shores,one from nature, not humans-an avian flu pandemic.Now we face with shock such kind of catastrophe that the century have never experienced,covid-19,Corono virus.
Corona viruses are a group of related viruses that cause diseases in mammals and birds. In humans, corona viruses cause respiratory tract infections that can range from mild to lethal. Mild illnesses include some cases of the common cold (which has other possible causes, predominantly rhinoviruses), while more lethal varieties can cause SARS, MERS, a Corona viruses constitute the subfamily Orthocoronavirinae, in the family Coronaviridae, order Nidovirales, and realm Riboviria. They are enveloped viruses with a positive-sense single-stranded RNA genome and a nucleocapsid of helical symmetry. The genome size of coronaviruses ranges from approximately 26 to 32 kilobases, one of the largest among RNA viruses. They have characteristic club-shaped spikes that project from their surface, which in electron micrographs create an image reminiscent of the solar corona from which their name derive.
Coronaviruses were first discovered in the 1930s when an acute respiratory infection of domesticated chickens was shown to be caused by infectious bronchitis virus (IBV).[9] Arthur Schalk and MC Hawn described in 1931 a new respiratory infection of chickens in North Dakota. Human coronaviruses were discovered in the 1960s. The earliest ones studied were from human patients with the common cold, which were later named human coronavirus 229E and human coronavirus OC43. They were first imaged by Scottish virologist June Almeida at St. Thomas Hospital in London.
ETYMOLOGY
The name "coronavirus" is derived from Latin corona, meaning "crown" or "wreath", itself a borrowing from Greek κορώνη korṓnē, "garland, wreath". The name was first used in 1968 by an informal group of virologists in the journal Nature to designate the new family of viruses. The name refers to the characteristic appearance of virions (the infective form of the virus) by electron microscopy, which have a fringe of large, bulbous surface projections creating an image reminiscent of a crown or of a solar corona. This morphology is created by the viral spike peplomers, which are proteins on the surface of the virus.
STRUCTURE
Coronaviruses are large pleomorphic spherical particles with bulbous surface projections. The average diameter of the virus particles is around 120 nm (.12 μm). The diameter of the envelope is ~80 nm (.08 μm) and the spikes are ~20 nm (.02 μm) long. The envelope of the virus in electron micrographs appears as a distinct pair of electron dense shells.
EVOLUTION
Origins of human corona viruses with possible intermediate hosts.
The most recent common ancestor (MRCA) of all corona viruses is estimated to have existed as recently as 8000 BCE, although some models place the common ancestor as far back as 55 million years or more, implying long term coevolution with bat and avian species. The most recent common ancestor of the alphacoronavirus line has been placed at about 2400 BCE, the beta corona virus line at 3300 BCE, the gammacoronavirus line at 2800 BCE, and the delta coronavirus line at about 3000 BCE. Bats and birds, as warm-blooded flying vertebrates, are an ideal natural reservoir for the coronavirus gene pool (bats the reservoir for alpha coronavirus and beta coronavirus – and birds the reservoir for gammacoronavirus and deltacoronavirus). The large number of host bat and avian species, and their global range, has enabled extensive evolution and dissemination of coronaviruses.Unlike other betacoronaviruses, bovine coronavirus of the species Betacoronavirus 1 and subgenus Embecovirus is thought to have originated in rodents and not in bats. In the 1790s, equine coronavirus diverged from the bovine coronavirus after a cross-species jump. Later in the 1890s, human coronavirus OC43 diverged from bovine coronavirus after another cross-species spillover event.
RISK OF CORONO VIRUS
Coronaviruses vary significantly in risk factor. Some can kill more than 30% of those infected, such as MERS-CoV, and some are relatively harmless, such as the common cold. Coronaviruses can cause colds with major symptoms, such as fever, and a sore throat from swollen adenoids. Coronaviruses can cause pneumonia (either direct viral pneumonia or secondary bacterial pneumonia) and bronchitis (either direct viral bronchitis or secondary bacterial bronchitis). The human coronavirus discovered in 2003, SARS-CoV, which causes severe acute respiratory syndrome (SARS), has a unique pathogenesis because it causes both upper and lower respiratory tract infections.
Six species of human coronaviruses are known, with one species subdivided into two different strains, making seven strains of human coronaviruses altogether. Four of these coronaviruses continually circulate in the human population and produce the generally mild symptoms of the common cold in adults and children worldwide: -OC43, -HKU1, HCoV-229E, -NL63. Coronaviruses cause about 15% of commons colds. The majority of colds are caused by rhinoviruses.The four mild coronaviruses have a seasonal incidence occurring in the winter months in temperate climates. There is no preference towards a particular season in tropical climates.
MEDICINE
There are no specific vaccines or medicines for COVID-19
PRECAUTION
STAY home
KEEP a safe distance
WASH hands often
COVER your cough
 സാങ്കേതിക പരിശോധന - jayasankarkb തീയ്യതി: 28/ 04/ 2020 >> രചനാവിഭാഗം - ലേഖനം
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