Infected houses never happened?

 The Netziv notes that we have the famous statement of the Rashby that houses were infected as a present from G-d to reveal the hidden treasures and we have the contrary statement from his son that there never was an infected house

He concludes that this halacha is actually concerned with describing the proper foundation of a Jewish home, the Caanites were merchants who as a class are prone to lashon harah, slander etc etc - as opposed to farmers. So their houses were built on immoral foundation also on idolatry. The halacha advises removing (when possible) the moral decay and replacing it with a holy foundation. However sometimes the structure needs to be totally replaced. That is why only a cohen can decided whether the infection is impure and not a talmid chachom

Interestingly the Rambam also says it is a miraculous sign indicating spiritual impurity