There are many reasons why some people seem to get lice repeatedly. They may have not eradicated the first outbreak completely. If the lice were not removed from their living space, they may be re-infested. Studies have shown that head lice leave a scent that is attractive to other head lice—this is one reason to be extra diligent in rechecking someone for three months after the outbreak.
No. The only difference a warmer climate makes is the lice are more apt to move up and down the hair shaft and lay eggs throughout the hair, while in colder climates, they generally stay closer to the scalp.
Anyone, including african americans, can get head lice. They are less likely to get head lice because of the shape of their individual hair strands but they are far from immune.
Everyone is at risk. If you have contact with an infected person, you can get them.