Risk-factor studies as an epidemiologic tool.

Anecdotal and historical data strongly suggest that environmental factors and hygienic practices play a major role in chlamydial transmission and the maintenance of endemic blinding trachoma. They also suggest that relatively minor alterations in these practices can have a profound impact, virtually eliminating trachoma as a blinding disease. This is especially critical, since few countries can now afford extensive, ongoing chemoprophylaxis programs. Epidemiologic studies are now needed to identify the critical risk factors in each affected culture. A recent study that used this approach found that in one region the simple hygienic practice of face washing was strongly associated with trachoma status. The next task will be to carry out appropriately designed intervention trials to establish the significance of such a factor and the possibility of altering it.