Define Corona Virus ? and its history (50 words min)
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Answer:
On 31 December 2019, the World Health Organization (WHO) was formally notified about a cluster of cases of pneumonia in Wuhan City, home to 11 million people and the cultural and economic hub of central China. By 5 January, 59 cases were known and none had been fatal.1 Ten days later, WHO was aware of 282 confirmed cases, of which four were in Japan, South Korea and Thailand.2 There had been six deaths in Wuhan, 51 people were severely ill and 12 were in a critical condition. The virus responsible was isolated on 7 January and its genome shared on 12 January.3 The cause of the severe acute respiratory syndrome that became known as COVID‐19 was a novel coronavirus, SARS‐CoV‐2. The rest is history, albeit history that is constantly being rewritten: as of 12 May, 82,591 new cases of COVID‐19 worldwide were being confirmed daily and the death rate was over 4200 per day.4
Coronaviruses in man
Phylogenetic analysis suggests that SARS‐CoV‐2 originated in animals, probably bats, and was transmitted to other animals before crossing into humans at the Huanan wet market in Wuhan City.5, 6 There is some evidence that the intermediate vector may have been pangolin, a type of nocturnal anteater imported illegally for its flesh. This animal carries a coronavirus that is very similar to SARS‐CoV‐2 but differs in a crucial region that determines viral infectivity and host range. It is therefore possible that the virus passed into humans and then, through adaptation as it infected more people, mutated to acquire the characteristics that made it spread so quickly.
SARS‐CoV‐2 is not the first coronavirus to cause outbreaks of respiratory infection in humans. Six others have been identified so far, all believed to have originated in animals.6, 7 The four coronaviruses that are now endemic in humans cause 10–15% of common colds, mostly peaking between December and April in temperate climates.8 NL63 and 229E probably came from bats; OC43 and HKU1 seem to have originated in rodents. Each of these causes mild symptoms, though OC43 has ancestry as a bovine coronavirus that may have caused a pandemic at the end of the 19th century.
Two non‐endemic coronaviruses have caused serious disease. SARS‐CoV was the first to be recognised, occurring first in November 2002 in China (though not known at the time) and coming to the attention of WHO early in 2003 in Viet Nam.9 The outbreak was largely over by July, and the last cases were reported in China in April 2004. This virus was responsible for Severe Acute Respiratory Syndrome (SARS), a flu‐like illness, though diarrhoea was common. It could progress to pneumonia and respiratory failure in two weeks and 25% of people infected required intensive care. A total of 8098 cases and 774 deaths were notified.10 SARS‐CoV appears to have originated in horseshoe bats and possibly transmitted to humans via palm civet cats, traded in China for their meat.
The second serious infection due to a coronavirus was Middle Eastern Respiratory Syndrome (MERS). The MERS‐CoV virus was first identified as the cause of a fatal infection in Saudi Arabia in 2012.11 It spread to 27 countries. Unlike SARS, MERS is still prevalent and, as of November 2019, 2494 infections had been notified, of which 858 proved fatal.12 Like SARS, MERS causes a flu‐like illness with symptoms ranging from mild (with about one‐quarter of people also having diarrhoea) to severe pneumonia, acute respiratory distress syndrome, septic shock and multiorgan failure. MERS‐CoV is believed to have reached humans via dromedary camels, which appear to be a reservoir in several Middle East states. The original source species is not known, but bats are the most likely.
Explanation:
Coronavirus disease (COVID‐19) is now dominating the lives of everyone, and its history is constantly being rewritten. This article gives a brief account of the story so far: where SARS‐CoV‐2 might have originated, how it compares with other viruses that cause major respiratory disease, and some of the treatments and vaccines currently being investigated to combat it.