Decline of the new Swedish variant of Chlamydia trachomatis after introduction of appropriate testing.

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.