The current Coronavirus (COVID-19) epidemic is generally believed to have started in Wuhan, China, late in 2019. From there, it spread throughout the world, forcing countries into lockdown, killing thousands and generally stopping world travel and trade.
But what is it? And why does it have two names – Coronavirus and COVID-19?
Coronavirus is actually a family of viruses. They were first identified in the 1930s but weren’t given the ‘coronavirus’ name until the 1960s, when electron microscope images of the viruses showed a ‘crown’ (Latin – corona) or a large fringe of projections around the virus, similar to the ‘halo’ or ‘corona’ around the sun.
Tracing the virus back, it seems likely that coronaviruses originated in bats and birds as long ago as 3000 BC. The first one identified in modern times was Avian Infectious Bronchitis in chickens, described in 1931. Two more were identified in the 1940, Mouse Hepatitis Virus and Transmissible Gastroenteritis Virus, which affected pigs, though, at the time, the thee viruses weren’t identified as being related.
The first coronaviruses to affect humans were identified in the 1960s. Three scientists working at the Common Cold Unit of the British Medical Research Council isolated a common cold virus in 1960 that couldn’t be cultivated using methods that normally worked for previously identified cold viruses. At the same time, scientists working at the University of Chicago also identified a new cold virus that needed special methods of cultivation.
Today, seven variants of coronavirus that can infect humans have been identified, two of which are related. Four cause symptoms of the common cold – 30 per cent of colds are now thought to be caused by one of these four coronaviruses.
The other three are much more serious.
Severe acute respiratory syndrome (SARS-CoV) first occurred in Guangdong Province, China, in November 2002, but the patient died before its significance could be realised. The Chinese government first notified the World Health Organisation (WHO) of the outbreak in February 2003. By the time the outbreak ended in 2005, 8,000 people had been infected, just under 10% of whom had died. Scientists finally traced the source to cave-dwelling horseshoe bats in Yunnan province which had passed the disease to civet cats and thence to humans after the cats were sold in local meat markets.
Middle East respiratory syndrome-related coronavirus (MERS-CoV) was first reported in 2012 in Saudi Arabia and infects humans, bats and camels. By 2015, the virus had been reported in 21 different countries. It was particularly lethal – of the nearly 3,000 confirmed cases, 850 (37%) died.
SARS-CoV-2 is genetically 70% identical to the original SARS-CoV virus and has a 96% similarity to a bat coronavirus – the likely source. It first occurred as a pneumonia outbreak in Wuhan province, China, in December 2019 and was identified as a new coronavirus on 31 December 2019. The name COVID-19 (Corona Virus Disease 2019) was coined by the WHO on 11 February 2020. By 29 April 2020, over three million people had been diagnosed with the disease of which some 217,000 had died, a fatality rate of around 7%.
Perhaps giving a clue to the disease’s source, cats and ferrets have been found to be susceptible to the disease. A domestic cat in Belgium and tigers in Bronx zoo in the USA have been diagnosed with the disease, as have farmed minks in the Netherlands. Bearing in mind that the original SARS outbreak began with civet cats, perhaps a similar transfer took place this time.
So, there is the explanation. Coronavirus is the family of viruses. The particular one causing the current epidemic is SARS-CoV-2 and the disease that humans are suffering is COVID-19. It started in bats, possibly transferred through cats or ferrets or similar, and reached humans at the end of 2019. There is, as yet, no cure or immunisation, so everyone is being urged to stay indoors, stay separate and stay safe!