I'm not familliar with the life-cycle of the disease. Where do the mosquitoes get it?
I don't know, but post #49 has info that's helpful.
I know it isn't contagious because I had it once, and it's nasty; had a temperature of over 104 at one point. I lost about 10 pounds in a little more than a week. I got it in Pago Pago, American Samoa, 1975. Just to be sure, I did an internet search to see if the doc who treated me and told me it wasn't contagious was correct. He was.