I'm Hispanic, and I grew up in Texas. It is still a belief among some hispanics. Just like all cultures, there are customs and beliefs that betray common sense.

My grandmother was the local neighborhood "Curandera", or healer. This was not some border town neighborhood, it was a suburb of Dallas. Many times as a child with a cold or flu or whatever, a ritual was performed at my bed involving an egg, broom straws floated on the egg in the shape of the trinity, and a bunch of bible reading and incantations. Did it work? Beats me, but it was creepy.