C. trachomatis strains are generally divided into three biovars based on the type of disease they cause. These are further subdivided into several serovars based on the surface antigens recognized by the immune system. Serovars A through C cause trachoma, which is the world's leading cause of preventable infectious blindness.Burton, Matthew J.; Trachoma: an overview, British Medical Bulletin, Volume 84, Issue 1, 1 December 2007, Pages 99–116, https://doi.org/10.1093/bmb/ldm034 Serovars D through K infect the genital tract, causing pelvic inflammatory disease, ectopic pregnancies, and infertility. Serovars L1 through L3 cause an invasive infection of the lymph nodes near the genitals, called lymphogranuloma venereum.
