yes, you understood what was the joke about. thanks for elaborating it.:-D

it's a joke.

A village Boy was leaving for the city for the very first time.
Father of village boy: Son you are going to city for the very first time so I must tell you to be very alert to keep distance from city girls, there is very dangerous disease called AIDS which city people suffer. if you come in contact with a city girl, you may get AIDS,from you, your wife will get AIDS, from your wife I will get AIDS, from me, your mother will get AIDS, and from your mother, eventually the whole village will be caught with AIDS.