COVID19 has an unprecedented range of symptoms from none to total organ necrosis and failure. It has a transmission mechanism that has never been seen before in humans, where it forces cells to grow a tubule and penetrate the walls of nearby cells to spread beyond the reach of the immune system, and it can infect the immune system like HIV. It has an unprecedented inter-species range, so it can harbor in our communities outside of humans.
There are signs that it can remain endemic, and the mortality rate and permanent damage is higher than other endemic diseases. It scares and surprises doctors who worked on HIV, SARS, MERS and Ebola. It has sickened and killed more medical workers than other infections.
From this radical number of "gains of functions" the chances it arose naturally are near zero. On the other hand, it was not produced by sequencing or CRISPR, so coronavirus researchers can claim "it was not engineered" just like President Clinton claimed oral sex was not sex.
This means it was A PREDICTABLE ACCIDENT, as if a person drank a bottle of whiskey and then tried to drive a motorcycle down a mountain on a twisty road with black ice every Friday night with saddle bags full of blasting caps.
So what am I basing these claims on?
I did a search for papers authored by Zhengli Shi in online pubs and read a dozen abstracts that show the progress of her research with researchers from the Wuhan Institute of Virology, and some crediting funding from Dr. Fauci's NIAID. They collected Horseshoe bats and Horseshoe Bat viruses from the caves in southern China, also Pangolins and Civet Cats and ran the coronaviruses back and forth which gave them the spike protein and extreme heat resistance and the ability to infect many species. Most adult human cells have ACE receptors, which is the binding site that attaches and activates the virus to inject RNA.
The problem is that the majority of papers published in mainstream journals like NEJM, for example, are either biased corporate researchers or incompetents trying to advance their career. Nearly all science news writers are less thorough, and don't take motivation into account, but are swayed by politics and wishful thinking.
The fundamental principle is GENETICS ARE FAR TOO COMPLEX FOR HUMANS TO MANIPULATE. Once you understand WHY this is true, then you know that you can't accept the conclusions and protests of anyone who manipulates genes for a living - if they understood that their work was guaranteed to explode in their face, they would not be doing it.
My reference for this conclusion is "Arrival of the Species" by Andreas Wagner. This explains in great detail how evolution works on a genetic level, based on brilliant computer modelling and Monte Carlo methods. It is difficult to have a detailed argument without this body of knowledge.