Flies In Danang

Has anyone else noticed a recent increase in flies here in Đà Nẵng?

I've gotten pretty good at minimizing flying insects in my lodgings by closing windows and doors just before sunset, then opening everything up for fresh air at sunrise.

However, in the last week or so, the flies are everywhere, all the time.

Even my usually unflappable Vietnamese friends can often be seen shooing the bugs from all over their bodies.

I'm talking about flies, not mosquitoes or "no-see-ums".

We haven't had significant rain now for a few weeks, so I'm guessing that might be a factor.

I'm pretty sure the housekeepers sprayed for them yesterday (I'm back at the hotel) because this morning they were scattered on the floor between the curtains and the French doors.

https://gordythomas.files.wordpress.com/2019/02/20190218_094757-01.jpeg
Of course, the moment I opened French doors this morning, a few new flies flew into the room.

They don't bother my skin much. Probably because I use a citronella/onion spray on my arms and legs, and regularly apply tea tree oil to my bald head and acne-prone neck.

EDIT:

The housekeeper did spray yesterday. I was pretty sure, as I'd seen her spray a few months back when I complained about mosquitoes.

Also, it's not just my neighborhood. I've noticed this at various locations in Đà Nẵng.

I think it may have to do with the coming of Spring. Flies, dragonflies, crickets, beetles, roaches, etc. seem to appear/be most active during the coming months.