How Did Covid-19 Start And What Exactly Is Covid-19?

The disease appears to have originated from a Wuhan seafood market where wild animals, including marmots, birds, rabbits, bats and snakes, are traded illegally. Coronaviruses are known to jump from animals to humans, so it’s thought that the first people infected with the disease – a group primarily made up of stallholders from the seafood market – contracted it from contact with animals.

The hunt for the animal source of Covid-19 is still unknown, although there are some strong contenders. A team of virologists at the Wuhan Institute for Virology released a detailed paper showing that the new coronaviruses' genetic makeup is 96 per cent identical to that of a coronavirus found in bats, while a study published on March 26 argues that genetic sequences of coronavirus in pangolins are between 88.5 and 92.4 per cent similar to the human virus. Some early cases of Covid-19, however, appear to have inflicted people with no link to the Wuhan market at all, suggesting that the initial route of human infection may pre-date the market cases.

The Wuhan market was shut down for inspection and cleaning on January 1, but by then it appears that Covid-19 was already starting to spread beyond the market itself. On January 21, the WHO Western Pacific office said the disease was also being transmitted between humans – evidence of which is apparent after medical staff became infected with the virus.

Coronaviruses are a large group of viruses that are known to infect both humans and animals, and in humans cause respiratory illness that range from common colds to much more serious infections. The most well-known case of a coronavirus epidemic was Severe Acute Respiratory Syndrome (Sars), which, after first being detected in southern China in 2002, went on to affect 26 countries and resulted in more than 8,000 cases and 774 deaths.

While the cause of the current outbreak was initially unknown, on January 7 Chinese health authorities identified that it was caused by to a strain of coronavirus that hadn’t been encountered in humans before. Five days later the Chinese government shared the genetic sequence of the virus so that other countries could develop their own diagnostic kits. That virus is now called Sars-CoV-2.

Although symptoms of coronaviruses are often mild – the most common symptoms are a fever and dry cough – in some cases they lead to more serious respiratory tract illness including pneumonia and bronchitis. These can be particularly dangerous in older patients, or people who have existing health conditions, and this appears to be the case with Covid-19. A study of 44,415 early Chinese Covid-19 patients found that 81 per cent of people with confirmed infections experienced only mild symptoms. Of the remaining cases, 14 per cent were in a severe condition while five per cent of people were critical cases, suffering from respiratory failure, septic shock or multiple organ failure. In the Chinese study, 2.3 per cent of all confirmed cases died, although the actual death rate is probably much lower as many more people will have been infected with the virus than tested positive.