Objective: The longitudinal epidemiological development of the new variant of Chlamydia trachomatis was studied after appropriate testing procedures had been introduced when the strain was detected in 2006.
Methods: The number of cases of the new variant of C trachomatis was followed from 2007 through 2011 from the laboratory records. Testing for C trachomatis is centralised to one laboratory with around 80-85 000 persons being tested annually in a population of 1.1 million.
Results: During the 5-year period, 410 973 patients were tested of which 25 723 cases were positive. The proportion of the new variant of all positive cases declined from 30% in 2007 to 6% in 2011. While the number of the new variant of C trachomatis declined, the ordinary wild-type strains remained largely unchanged.
Conclusions: A selective decline of the new variant of C trachomatis has occurred after appropriate laboratory testing was introduced. A new balance point between 5% and 10% for the new variant seems to be gradually approached.