The burden of trachoma for a community is heavy: human suffering requiring treatment and assistance, and a severe handicap for education and work. Trachoma can be transmitted by direct or indirect contact. Overcrowding, lack of clean water, and unsanitary habits all contribute to its spread. Repeated exposure to infection, reinfections and relapses play a role in increasing the severity of the disease. This chronic infection is caused by micro-organisms [Chlamydia] which are very similar to bacteria but which, like viruses, are intracellular parasites. The clinical manifestations of trachoma range from a severe disease causing blindness, to a relatively mild condition which evolves towards spontaneous cure.