Only minor changes in the incidence of chlamydia

Recent numbers from Statens Serum Institut (SSI) reveal that slightly more persons had chlamydia detected in 2018 than in 2017. This is due, in part, to the fact that slightly more people were tested in 2018 than the previous year, but the positive rate was slightly lower.

In 2017, slightly fewer cases of chlamydia were detected than in 2016, but in 2018 the trend had changed: Now an increase was observed.

According to the latest numbers from Statens Serum Institut (SSI), a total of 33,415 chlamydia cases were detected in 2018 compared with 32,931 cases in 2017. This corresponds to a slight 1.5% increase.

The positive rate declined slightly

Normally, the increasing number of chlamydia cases is explained by the fact that more people are being tested - and consequently more cases of infection are detected.

This explanation may also apply to the 2018 figures.

This is so because more people were tested for chlamydia last year than in 2017, a total of 275,760 persons in 2018 compared with 267,862 the year before - corresponding to a 2.9% increase.

And as the increase in the number of tested persons is larger than the increase in the number of positives, the positive rate has declined slightly from 12.3% to 12.1% of those tested.

More 15-29-year-olds tested

In the share of the population that is most heavily affected by chlamydia - young people aged 15-29 years - both sexes recorded a clear increase in the number of persons who were tested in 2018 compared with 2017.

“This is an encouraging trend, which we hope will continue in years to come,” notes Head of Unit Steen Hoffmann from the SSI.

In 2018, slightly fewer very young girls, aged 10-14 years, were tested than in 2017 - 295 per 100,000 (compared with 310 per 100,000 in 2017). Among those tested, 14.1% and 14.5%, respectively, had positive chlamydia tests, so the share remained practically stable.

The figures also show that in the 40+ age group, a larger than normal share of women undergo chlamydia testing. Here, the positive rate is as low as 2-3%.

More men need to be tested

According to the SSI, there is a need to test more men - young men in particular.

“Thus, in 2018 men still only comprised 41% of the chlamydia cases detected, even though the share of positive samples among men is far higher than among women,” notes Steen Hoffmann.
The SSI’s statement of detected chlamydia infections is based on data from The Danish Microbiology Database (The MiBa). The MiBa comprises all positive and negative results from chlamydia tests.

For more information, please see EPI-NEWS 

Read the 2018 annual chlamydia report

Facts about chlamydia

  • Chlamydia is the name of a sexually transmittable infection caused by the bacterium Chlamydia trachomatis.
  • The condition spreads through unprotected sex. Spreading occurs among heterosexuals as well as among men who have sex with men (MSM).
  • The number of chlamydia cases increased constantly from 2000 (14,785 cases) until 2009 (29,786 cases). Then followed a slight decrease until 2012, after which the number of cases has, once again, increased every year until 2018, except for the decrease recorded in 2017.
  • For both sexes, the overwhelming majority of chlamydia cases is observed among young people aged 15-29 years. In 2018, 80% of the male chlamydia cases occurred in this age group as did 88% of the female chlamydia cases. This distribution has remained completely unchanged for many years.