Which fallacy is committed in the following statement? 'People with cases of flu should be kept in quarantine, because it has never been disproven as the best means of keeping the disease from spreading.'

The claim rests only on the fact that quarantine has never been disproven, an appeal to ignorance.

Not being shown false is treated as if it were positive proof.

Absence of refutation is not evidence that a claim is true.

The burden of proof is wrongly shifted onto the doubter.

This is the appeal to ignorance (argumentum ad ignorantiam).