https://www.aero-sense.com/en/asd-aircraft-insecticide

They've been spraying on flights to and from India for many years, at least back into the 90s if I recall correctly.

They spray it into the air - not directly onto the passengers. And it's not anti viral.

The announcement the OP quotes is strange, I've been on flights where the spray has been required dozens of times and have never heard it announced this way.

It's more like - We are required to spray this insecticide. If you have contacts or you think your eyes may be bothered close them for a few seconds after we pass by.....