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STI trends in Europe: chlamydia rates stabilise while gonorrhoea numbers go up

17 Sep 2015

With an estimated 146 million infections each year, chlamydia is the most common sexually transmitted infection worldwide. And Europe is no exception with almost 385 000 cases reported in 2013 alone and more than 3 million between 2004 and 2013. But while trends in the number of chlamydia infections appear to have stabilised in recent years, gonorrhoea rates have gone up by 79% since 2008, particularly among men.

The new ECDC report Sexually transmitted infections in Europe 2013 covers data and trends on the five sexually transmitted infections (STI) under surveillance in the countries of the European Union and European Economic Area (EU/EEA): chlamydia, gonorrhoea, syphilis, congenital syphilis and lymphogranuloma venereum (LGV).

The data show that different age groups are affected by different STI across the countries of the European Union and European Economic Area: while young adults between 15 and 25 years of age are only 14% of all syphilis cases, they account for almost 39% of gonorrhoea and 67% of chlamydia cases in 2013. This not only reflects the prevalence of the diseases but also testing and screening practices targeted at sexually active young adults, particularly for Chlamydia trachomatis infections.
 
Since 2008, the overall numbers for gonorrhoea have shown an upturn by 79%, particularly among men (+95%). This rise seems to be linked to increased cases numbers among men who have sex with men (MSM). The overall syphilis rate has been going up since 2010, particularly among men.
 
Chlamydia
In 2013, 384 555 cases of chlamydia infection were reported in 26 EU/EEA Member States translating into an overall rate of 182 notifications per 100 000 population. Two-thirds (67%) of all chlamydia infections were reported in young people between 15 and 24 years of age, with the highest rates reported among women aged 20 to 24 years (1 717 cases per 100 000 population).
The high rates of chlamydia among young women (207 per 100 000 population) illustrate that some countries are successfully implementing effective case detection and management in an attempt to reduce the likelihood of reproductive tract complications from the infection.
 
But consistently high chlamydia rates also suggest that there is little, if any, effect of current chlamydia control activities on overall prevalence. The true incidence of chlamydia is likely to be considerably higher, due to the asymptomatic nature of the infection. In addition, considerable differences in testing methods, coverage and surveillance systems across Europe mean that many infections are not diagnosed or reported.
 
Gonorrhoea
In 2013, 52 995 gonorrhoea cases were reported in 28 countries of the EU/EEA – 61% of all cases were reported by the United Kingdom alone. Gonorrhoea was reported three times more often in men than in women and nearly half of all gonorrhoea cases in 2013 (43%) were reported in MSM. Since 2008, the overall rate has gone up by 79%, and trends show an increase in most EU/EEA Member States.
 
The rising rates of gonorrhoea in many countries, although affected by increased testing among at risk groups, indicate on-going unsafe sexual behaviour – which also carries the risk of transmission of other STI, including HIV. In addition, the increased number of cases is worrying because of the possibility of antimicrobial-resistant N. gonorrhoeae strains. The latest resistance data from the European Gonococcal Antimicrobial Surveillance Programme suggest stable levels of resistance to cefixime and no significant increase in resistance to ceftriaxone. Despite these data, the development of resistance to existing treatments is feared to be only a matter of time.
 
Syphilis and congenital syphilis
A total of 22 237 syphilis cases were reported in 2013 (5.4 notifications per 100 000 population); five times more often in men than in women. Only 14% of cases reported in 2013 were among young adults between 15 and 24 years of age; the majority of cases were reported in people 25 years and older (30% among 25 to 34-year-olds; 27% among the 35 to 44-year-olds and 29% among the 45-year-olds or older). Most countries reported increasing trends between 2008 and 2013.
 
In 2013, 64 cases of congenital syphilis were reported in nine countries; thirteen countries reported zero cases. All EU/EEA countries have case report rates below the World Health Organization’s target for elimination of congenital syphilis. The effectiveness of national syphilis antenatal screening programmes is being investigated in an ECDC project.
 
Lymphogranuloma venereum
In 2013, 1 043 cases of lymphogranuloma venereum (LGV) were reported in 10 countries.
 
 
For all five STI, the numbers of reported cases are most likely only a fraction of their true incidence due to lack of diagnosis or reporting. This is why strengthening enhanced surveillance of STI in Europe is essential to provide the necessary information to monitor disease distribution and evaluate the public health response to prevent and control the transmission of infections.
 
 

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