Headlice crawl from head to head. Because young children are often in close proximity to one another in play or classwork, or in close proximity to family adults at home, headlice have opportunities to move from one head to another. It is impossible to know the origin of an outbreak. A less likely method of transmission is through the sharing of things like combs, hairbrushes, hats, and other things that touch the head and hair.
Because headlice need food, humidity and warmth to survive it is unlikely they will be found alive on car seats, curtains or carpets.
Adolescents and adults tend to spend little time in close proximity to others so transmission of headlice amongst older people is less likely than amongst the young