Ive been to Mexico several times. But my sister has them too and hasnt been there since we were kids and that was 25 years ago. Its possible that weve had these dormant for a long time. and when my immune dropped down thay attacked. You gave alot of good info too. I do believe they are hjhky contagious like pinworms. They spread real easy. If I touch my nose and touch my face somewhere they will spread there. They even tried to get a nest started on my index finger. I use this finger to pick at my face or my nose. Im going to print your info out and give it to the specialist I go and see.