Where did covid-19 come from? The question endures even now. The most accepted theory is that the virus jumped from animals to humans at a wet market in Wuhan, China. But the city also contains two laboratories focused on coronavirus research. Might it have leaked from one of them? The World Health Organisation says that investigations into the theory have not been extensive enough, and America’s intelligence agencies are divided over the two possibilities. But with China stonewalling investigations and withholding key data, it remains to be seen if the mystery of the origin of covid-19 will ever be solved.