American Diplomats Falling Ill in China after Hearing Noises

[Colorado Rambler]

I can't help but wonder if it's something like carbon monoxide - odorless, colorless and in less than lethal amounts, it can cause all the symptoms described. It can be very hard to diagnose someone suffering from chronic carbon monoxide poisoning because the symptoms can mimic those that arise from all sorts of other - generally more benign - conditions.

Whatever the reason, the problem is apparently real and the cause is extremely concerning and baffling.