“The only thing that can be said is that control measures have been successful in slowing its spread.”
Same thing I say about the garlic on my door. Never had a vampire at my house, not a single one!
I went to Yellowstone and received a flyer about avoiding buffalo because of the risk of getting gored. I hung it in my office, and am proud to say that not a single one of my employees was ever gored. Precautions work!