It seems that there are more cases of head lice during the school months but this is not because of a lice season. When children have more contact with each other, we see an increase in numbers. Many schools also enforce head lice policies, thereby increasing awareness of the problem.
An adult head louse can live on a person’s head for up to 30 days. They are not able to survive more than 48 hours off the head. A nit, separated from the head, will die. It needs the warmth of the body to incubate (much like a chicken sitting on an egg).
If the head lice are fertilized females, they may begin laying eggs immediately. Head lice generally travel in harems, often consisting of seven or eight females and one male. As females will lay eight to ten eggs daily, a simple case of head lice can escalate very quickly.
Since head lice have a low morbidity rate and are fairly host specific, the odds are low that they will spread disease. Some researchers believe that they carry disease, and studies are being done in that area to prove it.
A single female louse lays eggs twice a day and four to five eggs each time. Multiply that by 10, 20 or even 40 or more lice that might be on the head and it's easy to see how a severe infestation can develop quickly.