The 1977 H1N1 spread was never truly explained, here a possible lab incident in Russia was one of the possibilities:
https://journals.asm.org/doi/10.1128/mbio.01013-15?permanent...
The Coronavirus from Wuhan, China has a similar story, only this time it is in China.
https://www.reuters.com/business/healthcare-pharmaceuticals/...
To me a solid scientific explanation is still useful, e.g. the intimate study of the Wuhan lab into Coronavirus seems risky at best.