If you’re going to demand incontrovertible evidence that might never come up. But considering the scenario, viz. a cabal of careless scientists accidentally unleashed a plague that is killing millions , even the slightest hint of a cover up needs to be taken seriously.
Having worked with enough scientists I don’t for a moment doubt this hypothesis either. Ego and arrogance is what drives most of them, they’d rather choose self-perseverance over accidentally killing millions and go home to have lasagna as if it was just another Thursday without a sweat.