Can always be those, but I found the further into peri I climbed the more easily the migraines were triggered. You've been struck down with the flu, just the headache, temperature and congestion can tip you over the edge. It's a complete bummer!!
My visual auras, though infrequent, never last less than half an hour. Had to pull over when I was driving one day, central London on a red route where any stopping is illegal. A traffic warden came over and very kindly waited with me until it dissipated. Such a pain!
Effervescent is definitely the way to go! Hope you manage to bat this pesky flu off - it's certainly got a hold of you xx