Exactly. The comparison with Indonesia is interesting, which has a similar climate, but isn't as rich or developed as Singapore.

Air conditioning is actually very conducive to colds and the like. When you go from outside to inside you're usually sweaty and the air conditioning tends to make you too cold until you dry out. I've caught way more sniffles in the tropics than in the freezing climates.

Anecdotally, I flew from Bali to Singapore today and there seemed to be a lot more sniffles and coughing in Singapore. In Bali the architecture is very open with lots of fresh air, scooters being popular for transport whereas in Singapore they tend more to sitting together in air conditioned boxes of various types (buildings, busses etc).

The primary means of getting around in Singapore is public transportation (bus, train).

Public transit in SG is heavily air conditioned.

Air-conditioning also removes humidity from the air.

On a tangent, I'd love to see a graph of illnesses during summer before / after the widespread adoption of AC.

Someone could do a study of schools with broken ACs. That might be an easy way to study it.

I don't think a school would operate with broken AC

At least in the US plenty of schools in hot climates do not have A/C.

https://www.the74million.org/article/exclusive-too-hot-to-le...

Even those that do have A/C don't cancel class when it breaks.

https://www.floridatoday.com/story/news/education/2019/09/11...

The real takeaway from the 74 Million piece is that information about HVAC in American schools is difficult to come by. It would certainly be interesting to look at COVID-19 in schools vis-a-vis A/C, but good luck prying information from the school districts about either infections or air conditioning. Perhaps it would be easier in a tropical country like SG where A/C is more of a necessity than a luxury.

Most public schools in Singapore don't have A/C in most of their classrooms.

And circulated through the building via blowers.