Introduction:

  Coronaviruses are a group of RNA viruses with few of them causing the common cold in humans while others infect animals, including bats and pangolins. Scientists first identified a human coronavirus in 1965. Later that decade, similar human and animal viruses were named after their crown-like appearance. When virus infects, they attach to the cells, get inside them, and make copies of their RNA, which helps them to spread. If there’s a copying mistake, the RNA gets changed resulting in mutations. Researchers studied 103 samples of the new coronavirus collected from people, and they looked at coronaviruses from animals. Revealing that the coronaviruses found in humans weren’t all the same. Researchers found two of them and called “L” and “S” types. The S type came first. But the scientists say the L type was more common early in the outbreak being the dangerous one too. One may cause more disease than the other. Scientists need more data to really know what these strains mean to human health and COVID-19. Seven coronaviruses can infect humans. Scientists have divided coronaviruses into four sub-groups, like alpha, beta, gamma, and delta. Four common ones named as : 229E (alpha) , NL63 (alpha) ,OC43 (beta) ,HKU1 (beta). Three less-common ones as : MERS-CoV, a beta virus that causes Middle East respiratory syndrome (MERS) , SARS-CoV, a beta virus that causes severe acute respiratory syndrome (SARS) and SARS-CoV-2, which causes COVID-19. SARS-CoV emerged in southern China in 2002 and quickly spread to 28 other countries. Infecting more than 8,000 people and 774 died. There was also a small outbreak in 2004 involving only four more cases. This causes fever, headache, and respiratory problems such as cough and shortness of breath. MERS-CoV started in Saudi Arabia in 2012. Almost all of the nearly 2,500 cases have been in people who live in or travel to the Middle East. This was less contagious than SARS but more deadly, killing 858 people. It has the same respiratory symptoms but can also cause kidney failure. Together, they have caused more than 1600 deaths.  Now coming to the novel coronavirus SARS-CoV-2 that causes COVID-19. The “novel” coronavirus probability in animals is common but sometimes, a virus in animals crosses over into the humans. So this virus is not at all new to the world, but it is new to the human and as it was causing illness in humans in 2019, scientist named it as a novel coronavirus. Experts say that SARS-CoV-2 originated in bats which is also true for the coronaviruses behind MERS and SARS.  It is thought that the SARS-CoV-2 made the jump to humans at one of Wuhan’s open-air “wet markets.” Some wet markets sell wild or banned species like cobras, wild boars, and raccoon dogs. The crowded conditions cause the viruses to exchange genes from different animals. Sometimes the virus changes so much that it can start to infect and spread among people. The Wuhan market didn’t sell bats at the time of the outbreak. However, no definite proof that the virus jumped from bats to humans via an intermediary species has been found yet. That’s why early suspicion also fell on pangolins, also called scaly anteaters, which are sold illegally in some markets in China. Some coronaviruses that infect pangolins are similar to SARS-CoV-2. As SARS-CoV-2 spread both inside and outside China, it infected people who have had no direct contact with animals meaning that the virus is transmitted from one human to another. This growing worldwide transmission is now called a pandemic. WHO issued the official names COVID19 and SARS-CoV-2 on 11 February 2020. WHO chief Tedros Adhanom Ghebreyesus explained what COVID-19 stands for as : CO for corona, VI for virus, D for disease and 19 for when the outbreak was first identified (31 December 2019).   The virus is thought to be natural and has an animal origin, through spill over infection. The actual origin is still unknown, but it’s known that the first case seen in China. By December 2019, the spread of infection was entirely driven by human-to-human transmission. A study published in The Lancet January 2020 on the first 41 confirmed cases of  COVID19, , revealed the earliest date of onset of symptoms as 1 December 2019. Official publications of WHO reported the earliest onset of symptoms as 8 December 2019. Human-to-human transmission was confirmed by WHO and Chinese authorities by 20 January 2020. The transmission of the virus is through direct contact with respiratory droplets of an infected person, and touching surfaces contaminated with the virus. Though this virus survive on surfaces for several hours it can be killed by simple disinfectants. The symptoms generally include fever, cough and shortness of breath. More severe infection leads to pneumonia or breathing difficulties. Rarely, the disease can be fatal. These symptoms are very similar to the flu (influenza) or the common cold. Therefore testing is required to confirm COVID-19. It is of utmost importance to remember the key preventive measures being the frequent hand washing, wearing mouth mask and respiratory hygiene. The RT-PCR throat/swab test is the best for diagnosis of COVID-19.