AFAIK fomite transmission on public streets and other places sprayed by such "deep cleans" isn't a common spread vector for any widespread disease, so eliminating it can't make a meaningful difference.

Even fairly small changes can be significant with exponential feedback loops. That’s not to say they actually had any impact, just that you can’t always tell what was important.

For example it’s possible but unlikely that some other pandemic was accidentally prevented.

The flu is global, yes? How many cities did your "deep cleaning" (I've heard it for the first time)? Out of a total of how many cities? I decline your notion on those grounds alone.

Ehh... most viruses really don't live on surfaces very long. Unless they were continuously spraying the whole pandemic on a weekly basis I don't see how it could do much at all. And even if they were doing it every week... most of us get viruses from handled (by humans) surfaces.

Virus exist everywhere and is the most common entity on earth. In a tablespoon of seawater there can be ten million of them. Most are not dangerous to man, about 600 is known. They are also very good to survive on their own without a host and can live in most hostile environments.

Viruses aren't alive, and they certainly can't reproduce without host cells, so saying that they survive on their own doesn't seem like a terribly accurate statement. Trying to extend the metaphors of life "alive or dead, surviving" to viruses only generates misconceptions, instead "viable or inactivated" is a better way of looking at it.

Assuming what you're saying is correct (I don't know), what other effects does spraying disinfectants everywhere have?

I would be very surprised if doing this is a good idea, even if it kills covid and/or flu.

sunlight already good at kill virus, this have been knowen for many year. study find corona is dead from twenty minute sunlight alone: https://academic.oup.com/jid/advance-article/doi/10.1093/inf...

so maybe not so efective.

My guess is it had an effect for a few hours that day.

Probably not.