Global Spawn-Point Changes
Players across the globe have taken to The Silph Road's Reddit and other social media platforms during the afternoon of Wednesday, September 25, 2019 to report changes to many common spawn-points for Pokemon.
No official sources linked to Niantic or the Pokemon Company have currently commented regarding any changes, and no official channels have provided any form of confirmation as of yet, but the consensus among most players seems to be that many spawn points in the game have been added, changed, or even removed in some cases.
Update 9/27/2019
Niantic has officially addressed the changes to spawn points via their Twitter account
We're always looking for new ways to optimize the Pokémon GO experience for Trainers. To this end, we've recently updated where Pokémon can be encountered. We strive to improve with every change and thank you for your feedback. Stay tuned for more details.
— Niantic Support (@NianticHelp) September 27, 2019