Because much of China is in a subtropical climate - including Guangzhou - illness spread by mosquitoes is taken seriously. To this end, chemical spraying is done in many areas to keep the bugs under control, with extra attention paid to anywhere water may collect.

On the one hand, their strategy seems to work.  We are Minnesotans - instinctively able to hear mosquitoes, spot them, and squash them - and on our entire trip saw only one. That includes our day trip visit to a farming village, and over the whole week spent on Shamian Island.

On the other hand, what are they spraying, exactly, that does such an effective job?  I snapped this sign on Shamian, and later came across a spray crew on their rounds, dressed in face masks and latex gloves, misting the foliage, gutters, and drains along the street.

Since you’ll be exposed to the chemicals no matter what you do, be aware of what’s going on around you and try to stay away from freshly-sprayed surfaces. The threat of bug-borne disease is much more distinct than the effects of the limited chemical exposure you’ll encounter - that’s why you had all those inoculations before coming over.