Pretty sure Alejandro Mayorkas can ‘splain where it ultimately came from.
If you lay out the map....maybe 60-percent of the countries with Dengue Fever are in Central/South America. But it also shows up in China, Thailand, and India.
If you run a decent mosquito prevention program...the threat lessens. I might ask the question...does California have a program, or has it been outlawed?
I might add this footnote as well...if you live outdoors, in a crappy camp setting, with a ample population of mosquitos...it’s pretty good odds that you will develop Dengue Fever, and it will only be diagnosed when you are in the final week of life (too late to do much). So the homeless population will get the full thrust of the situation.