Indeed, where do pandemics come from?
First, there is some confusion about the name of this new virus. Sars-CoV2-19 is it correct name and even this name tells a story. Sars refers to what it causes - Severe Acute Respiratory Syndrome; CoV2, as its the second Coronavirus identified as causing this, and 19 as it was first identified last year. It's more commonly called COVID19, that is Coronavirus Disease 19.
The history of pandemics affecting the human race is a long one, though short when compared to how long we have been around. One of the first plagues was the plague of Justinian affecting the Byzantine empire and killing, over its two centuries of activity, an astonishing 25-100 million people in Europe. Since then there have been numerous pandemics with the Spanish Flu the most deadly early last century and HIV more recently. This century has already seen SARS (2003) and MERS (2012) and Ebola (2013) as well as the terribly sad Zika outbreak. Every episode has its own causes and conditions, but we can hardly claim not to have been warned.
Sars-CoV2-19 is the seventh coronavirus to affect humans, four of the others cause mild symptoms only.
All pandemics have certain phenomena in common. The keeping of animals in crowded conditions, dense human populations and travel.
THE ORIGIN OF COVID19:
It has either come from wild animals, mutating in the host before infecting humans, or infecting humans and mutating thereafter. Sars-C0V2-19, with its particular spikes which, rather unluckily, latch onto receptors in the cells lining the alveoli at far end of the airways, have not been found in these animals, but that is not to say they are not there as they are hosts to many similar viruses. Indeed, there are similar viruses in Pangolins with very similar spikes to those of Sars-Cov2-19.
This information comes from an excellent review in Nature, which concludes that the virus was unlikely to have come from accidental, or otherwise release from laboratories.
MERS was hosted in dromedary camels and then infected humans one by one with little onward transmission. Just as well as 35% of those infected with it died. Sars CoV1 originated in bats and spread to humans either directly or through animals sold in local markets.
Whether if jumped to humans in is deadly form, or mutated from a less deadly form in humans, the conditions for its spread were ripe.
Intensive unsustainable agribusiness in China, driven at least partially by western investment, has pushed traditional small farmers to specialise in the domestication and or capture of formerly wild animals, in this case bats or perhaps the rapidly disappearing pangolins, both already known to be the hosts of coronaviruses viruses. Sale of these ‘products’ in crowded, poorly regulated markets let this deadly genie forever out of the bottle. Densely populated cities, in this case Wuhan, ensured rapid initial spread and national and international travel did the rest. Crowding of animals, poor husbandry and lack of enforced regulation are behind so many epidemics.
After a dreadfully low start, which featured suppression of concerned voices form the front line, the Chinese acted quickly to aggressively lockdown the city and share the genome as soon as it was unravelled. No doubt poor decision making was driven by denial higher up the decision making chain. The penny soon dropped, partially driven by their recent experiences with Sars Cov1. They had some knowledge of what was about to hit them.
Their subsequent severe lockdown in affected areas reduced transmission and brought the outbreak under some degree of control, though I do not trust the news from China as there must surely be ongoing sporadic outbreaks due to returnees from abroad and inevitable loosening of control. It might be that these are being managed by aggressive testing, isolation and tracing. In this aspect of aggressive, early management and current decision making, S Korea is now the world’s leader, with their low mortality the prize of doing the right things promptly.
We also have to thank the Chinese for circulating details of the genome of the virus early in the history of this pandemic. This was not the case with SARS-Cov-1.
The rest is rapidly becoming history