Body lice infestation is found worldwide but generally is limited to persons who live under conditions of crowding and poor hygiene who do not have access to regular bathing and changes of clean clothes, such as:

• the homeless,
• refugees,
• survivors of war or natural disasters.

Infestations can spread rapidly under such conditions. Body lice infestation can occur in people of all races.

Body lice are spread through direct contact with a person who has body lice or through contact with articles such as clothing, beds, bed linens, or towels that have been in contact with an infested person. However, in the United States, actual infestation with body lice tends to be occur only in homeless, transient persons who do not have access to regular bathing and changes of clean clothes.

Body lice can transmit disease. Epidemics of typhus and louse-borne relapsing fever have been caused by body lice (typically in areas where climate, poverty, and social customs or war and social upheaval prevent regular changes and laundering of clothing).