you will do surgery on some of the 105 people. Some of them might die from complications, infections, etc or at least have lasting damage. Since several of the 5 people will not be any better off with treatment it's entirely possible that the screening produces palpably worse outcome.

The earlier you screen, the worse this is, since the ratio of false positives vs true positives gets higher and higher, for example 1000 vs 5 or 10000 vs 5.