Where did the virus causing the current pandemic come from? How did it get to a food market in Wuhan, China, from where it is thought to have spilled over into humans? The answers to these questions are gradually being pieced together, and the story they tell makes for uncomfortable reading.

Let’s start at the beginning. As of 17 March, we know that the Sars-CoV-2 virus (a member of the coronavirus family that causes the respiratory illness Covid-19) is the product of natural evolution. A study of its genetic sequence, conducted by infectious disease expert Kristian G Andersen of the Scripps Research Institute in La Jolla, California, and colleagues, rules out the possibility that it could have been manufactured in a lab or otherwise engineered. Puff go the conspiracy theories.