China denies the claim that these lab workers were sick at all. Even if they're lying, there is no proof they fell sick with Covid-19 and there is strong evidence they did not. All workers at the lab were later tested for Sars-CoV-2 antibodies and came up negative. Unless that's also a lie.

https://www.theguardian.com/world/2021/may/24/china-rejects-...

The bioengineering origin is, according to the overwhelming consensus of virologists, not plausible scientifically. It also requires a large and airtight conspiracy involving a number of respected scientists. Conspiracy theories are possible, but never parsimonious.

If we're going in for conspiracies, you should consider that the US intelligence community has a proven track record of lying for political gain. The Iraq War was started by a conspiracy.