I've counted three new cases on my route alone. Inspect your oaks now before it gets worse.
I was getting ready to climb an elm for a trim and tapped the trunk. It sounded hollow, so I drilled a test hole and found serious decay inside. If I had gone up, the tree could have failed under my weight. I changed plans and removed it from the ground instead. No one got hurt and the client understood why it had to come down.