No 36 - 2011

Chlamydia 2010

Chlamydia 2010

The laboratory notification system for chlamydia (oculogenital infection caused by Chlamydia trachomatis) receives quarterly data on laboratory diagnosed chlamydia from all departments of clinical microbiology and from two departments of clinical biochemistry (as from the second quarter of 2010, only one). 2010 saw the diagnosis of 27,932 chlamydia cases. This corresponds to an annual incidence of 505 per 100,000 (541 per 100,000 in 2009 and 532 per 100,000 in 2008). A total of 333,609 analyses were performed, and chlamydia was detected in 8.4% of those tested, Table 1.

The share of positives increased in the 2002-2008 period, while the 2009 level was in line with the share observed in 2008 (8.6%). In 2010, the share was marginally lower than the previous year. A total of 81% of males and 88% of females were aged 15-29 years (83% and 90%, respectively, in 2009), Table 2. The highest incidence among males was found among 21-year-olds, Figure 1.

In females, the highest incidence was found among 18-year-olds, in line with 2009. For both sexes, the incidences among the 17-, 18- and 19-year-olds were lower than in 2009, and for females this was also the case for the 20-23-year-olds. As in 2009, males constituted 38% of the diagnosed cases. This proportion has increased steadily from 23% in 1994.

Geographical distribution

Based on municipal code, chlamydia cases can be distributed on municipality, part of country and region. Table 3 presents the occurrence of chlamydia by part of country based on the municipal codes of the physicians who obtained the specimens for testing.


A total of 91% of the positive specimens were submitted by GPs, 9% by hospitals. All cases were detected using DNA amplification methods. Chlamydia was detected in urine samples in 9,413 cases, i.e. 34% of all cases (33% in 2009). Male samples constituted 88% of the positive urine samples (89% in 2009). Urine was used as sample material in 79% of the male chlamydia cases (78% in 2009). All laboratories reported positive findings in urine specimens. Rectal chlamydia was detected in 127 males (141 in 2009).

Chlamydia in children

Chlamydia was found in 257 children under 15 years of age (299 in 2009). Among these, 65 (25%) were under one year old, of whom 62 had conjunctivitis and two had chlamydia of the respiratory tract. Among 26 children under the age of one year with conjunctivitis for whom the age was stated in months, 24 were aged less than one month, one was 2 and one 3 months old. Urogenital chlamydia was detected in one girl aged 12 years, nine girls aged 13 years and 156 girls aged 14 years, and also in two 13-year-old and 22 14-year-old boys. The incidence among 10-14-year-old girls was 99 per 100,000 (127 in 2009), while the corresponding figure for boys was 14 per 100,000 (11 in 2009).


The number of chlamydia analyses was 4% lower in 2010 than in 2009, and the number of cases detected was 6% lower. Both the positive rate and particularly the incidence had decreased. This was a particularly clear trend in 17-19-year-olds of both genders. It is not known if this was caused by reduced disease occurrence or reduced sampling activity. The male proportion of the detected cases has levelled off at 38%, but there is no reason to believe that chlamydia is less prevalent among males than among females. The number of males in whom rectal chlamydia was detected decreased slightly. On detection of rectal chlamydia in males, testing for other sexually transmitted diseases should be considered, e.g. for lymphogranuloma venereum, gonorrhoea, syphilis hepatitis B and HIV.

(S. Hoffmann, Department of Microbiological Surveillance and Research)

7 September 2011