Like I mentioned in the blog ( what is head lice?) head lice do not jump or fly they just crawl really fast. So if two people are taking a selfie and the self takes about 8 seconds to take Lice can take about 3 seconds to crawl from one head to another. So they are pretty quick.
Children ( especially preschool and elementary age ) are the mostly people to get head lice because they do not have a concept of personal space.
But with the popularity of selfies I have seen a lot of teenage girls with head lice as well.