This is the first study presenting a description of the epidemiological and clinical characteristics of gonorrhoea cases diagnosed in a broad area in Spain. Its results help to characterise the most-at-risk groups for gonorrhoea infection in the country, and show differences by sex, transmission route and country of birth which should be taken into consideration when implementing control measures.
As shown by the high proportion of cases with previous STI episodes or concurrent STI, and the high HIV prevalence, individuals diagnosed with gonorrhoea in the EPI-ITS network are most likely at high risk of contracting and transmitting gonorrhoea, i.e. they are “core” populations for this infection. This result was to be expected given the characteristics of the participating clinics.
More than half of the cases occurred in MSM whereas, according to the Spanish Survey on Health and Sexual Behaviour (SHSB) (carried out in 2003 in a probability sample of the Spanish population), only 3.9% of men reported having had sex with other men at least once in their lifetime . Even if figures have changed since the survey was performed it is clear that there is an overrepresentation of MSM among gonorrhoea cases in our study, a result common with other studies performed in similar settings both in Spain (Madrid  and Barcelona ) and elsewhere . HIV prevalence among MSM was very high, 20.9%, although this figure is intermediate between the 31% found in the United Kingdom (UK)  and the 11% found in a Stockholm in studies performed in STI clinics . It is worrisome that most HIV-infected MSM were aware of their status before their gonorrhoea diagnosis, and yet they had not used condoms, a finding also described in other studies , which highlights the importance of continuous reinforcement of secondary prevention in MSM infected with HIV. The fact that in our study HIV prevalence is increasing only among MSM gonorrhoea cases adds urgency to this recommendation.
The percentage of rectal gonorrhoea among MSM found in our study is lower than reported in STI clinics in Germany and the UK (35% and 31% respectively) [16, 18]. Similarly, the proportion pharyngeal location (5.2%) is lower that the figures found in Germany (7.3%) , and in the Norwegian surveillance system (7%) . These variations could be due to differences in the study populations but, since both pharyngeal and rectal gonorrhoea are usually asymptomatic, our findings likely reflect low rates of screening in the MSM population, given that in our study the majority of MSM cases were symptomatic, or low rates of comprehensive and adequately tailored testing procedures.
The overrepresentation of foreigners among female patients is the consequence of the high proportion of sex workers among this group, since it is well known than around 90% of FSW in Spain were born out of the country . This is also the most likely explanation for the high proportion of concurrent STI diagnoses found in this and other Spanish studies [21, 22].
In spite of the high proportion of concurrent STI diagnoses among FSW with gonorrhoea in our study, HIV prevalence among them is quite low and, if compared with previous studies performed in FSW in Spain, remains stable [21–23]; this could be due, as has been found in other studies [21, 22], to high levels of condom use with clients, at least in vaginal sex, and/or to a low HIV prevalence among their clients. Pharyngeal gonorrhoea was very common among FSW in our study (53.1%), a result also found in other studies, which has been attributed to lack of consistent condom use for oral versus vaginal sex . It is also possible that frequent screening in the FSW population has contributed to the high proportion of the pharyngeal location.
Unprotected sex with casual partners was the most important source of infection in male patients. This finding has also been reported in Norway . These results are very important because they reflect a lack of risk perception in men and make it more difficult to conduct partner notification.
An important proportion of MSW in our study contracted gonorrhoea through sexual contact with a FSW. Results from the SHSB showed that 25.4% of men in Spain had had transactional sex in their lifetime, and 5.7% of them had done so in the previous 12 months; at the time of the survey, these were the highest proportions ever described in developed countries . Use of transactional sex was associated, among other factors, with age older than 25, low educational level and foreign origin, which are also common in our population. Interestingly, 95% of men who reported having paid for sex in the last 5 years in the SHSB also reported condom use in their last paid contact, which obviously has not been the case in our study. However, in the SHSB sexual contact was defined as penetrative sex (either vaginal, anal or oral), which is not the case in our study where 35% of male clients of FSW contracted the infection solely through oral sex, a situation in which condom use is less common.
Studies performed in other Western European countries found an important proportion of heterosexual males having been infected with gonorrhoea while abroad [19, 26, 27]. This is not the case in our study, where in all sex-transmission categories most infections were acquired within the country.
Foreigners are overrepresented in all sex-transmission categories, from a high of 57.9% in women to a low of 28.0% in MSM, comparing to the proportion of foreigners in the general population in Spain (14% in 2010). Latin-Americans are the main immigrant group in all categories, but the second group varies, reflecting different migration patterns among groups [19, 28].
This study has limitations. Variables such as educational level and probable source of infection have a substantial proportion of missing data. Furthermore, cases are not representative of all gonorrhoea cases in Spain, therefore the results can only be extrapolated to the setting from which the cases arose and not to the whole Spanish population. However, to our knowledge, most of the STI clinics operating in Spain belong to this network and cases included in this study represent more than one fourth of all gonorrhoea cases declared in Spain from 2006 to 2008.