People are infected by rubbing louse faecal matter or crushed lice into the bite wound or through scratching. The body louse lives in clothing and multiplies very rapidly under poor hygienic conditions. Lice proliferate rapidly in refugee camps and other crowded, unsanitary conditions and the risk can be expected to increase in rainy seasons, when more clothing and blankets are used. In 1996, Burundi reported 3,500 cases and that number jumped to 20,000 for the period from January to March 1997. Clinical diagnosis may be confirmed by serology.
Outbreaks occur in colder areas where people live in crowded, unhygienic, louse-infested conditions.
Patients are infective for lice during the febrile illness and possibly for two to three days after the temperature returns to normal. One attack usually confers long-lasting immunity. The easiest control method of occasional infestations is to expose infested clothing to a minimum temperature of 70 degrees C for at least one hour. In emergency situations, it may be impractical or impossible for people to wash properly and fuel for heating water may be in short supply. In general, chemical control is required, especially where louse-borne disease threatens.