Transmission dynamics in a population are dependent upon the rate of new infections of STIs (the reproductive rate), which is a function of the probability of transmission of a pathogen, the rate of partner change, and the duration of infectiousness [14]. The probability of transmission depends on individual factors such as risky sexual behaviour, virulence and efficiency of the organism and the duration of infection [15]. Based on mathematical models, the transmission probabilities of chlamydial infection, syphilis, chancroid and HSV-2 per unprotected sexual act (in a long-term relationship involving uncircumcised men) are estimated at 0.16, 0.18, 0.2 and 0.0009 for male-to-female transmission, and 0.12, 0.15, 0.2 and 0.00015, for female-to-male transmission, respectively, if neither partner is immuno-compromised [16]. The rate at which partners are changed and the probability of transmission can be targeted partly through preventive campaigns and partner notification. Since many STIs are easily curable, onward transmission can be prevented by prompt treatment of the infected (source) patient, tracing of partner(s) within a short period, and treatment of infected or exposed partners.

Not all individuals with an STI are aware of their infection, and an asymptomatic presentation is one of the reasons for the lack of awareness [17]. Amongst those aware of the STI, some seek treatment whilst others do not [9]. A cross-sectional study of residents in Lusaka in the 1990s showed diverse preferences when seeking care for STIs. These included traditional healers, chemists, and public and private health facilities [18]. Stigma, lack of privacy and confidentiality, the availability of other care options, and perceived poor quality of care, were among the factors impeding care-seeking for STIs from public facilities [18,19]. Early diagnosis and treatment of STIs is important for comprehensive management [20] and prevents further spread. Delayed care prolongs the duration of infection [14,21] and thus increases the likelihood of its secondary transmission and the occurrence of complications, such as still births or congenital infections (associated with a high mortality) [22].

The DHS data was based on 2-stage random cluster sampling. The sampling frame from the census of population and housing of Zambia for the year 2000 was used, which consists of >16,000 Standard Enumeration Areas (SEAs). A SEA is a small geographic unit consisting of 130 households on average. An urban–rural stratification was done for each of the 9 provinces of Zambia, making a total of 18 strata. In the first stage, 320 SEAs were sampled from these strata with proportional probability. In the second stage, 25 households were randomly picked from each selected SEA using equal probability systematic sampling. Men aged 15–59 and women aged 15–49years of permanent residence or visiting the night before were eligible for interview. The overall response rate was 98%. The interviews included various questions, however of interest to our study were the questions on demographic, socioeconomic position factors, episodes of genital ulcer in the previous year, and healthcare seeking related to these episodes. The socioeconomic position indicators included were education and wealth index. Wealth index was recorded from 5 to 3 categories i.e. poorest/poorer, middle and richer/richest. All respondents were asked to consent to HIV testing and one third to syphilis testing. Serial testing using 2 ELISA tests, Vironostika^® HIV Uni-Form II Plus O, Biomerieux and Anti-HIV 1/2 Plus, by Enzygnost^® Dade Behring, was done and Western Blot 2.2, Abbott Labs, as a tie breaker. For syphilis testing, Rapid Plasma Reagin was used for screening, and Treponema Pallidum Haemagluttination Assay as a confirmatory test. Further details are described elsewhere [23].

The age category with the highest estimate of GU symptoms in both men and women in the general population was 25–29years. This could reflect higher sexual activity in this age group although the risk remained significantly higher even after adjusting for some sexual behaviour characteristics. Some factors such as concurrency, frequency of sex or consistent use of condoms, however could not be adjusted for as they were not available, and thus could explain the persistent association.

Widowhood, separation or being divorced was also associated with GU symptoms in men, although this was not the case in women. It is possible that the widowed and separated/divorced engage in more risky sexual behaviour, putting them at risk of GUD, as seen in a Zimbabwean study where widows and widowers had more partners, a higher partner change rate and were likely to engage in transactional sex, compared to the non-widowed [24]. We also found that HIV prevalence was significantly higher among this group, which is in line with other studies [24-26]. This could be due to higher risky sexual behaviour among them or could arise from the fact that the most common cause of adult mortality in Sub-Saharan Africa is HIV. If the deceased spouse died of HIV, the widowed respondent would obviously be at increased risk of being infected too [24,27].

The prevalence of GUD was the same irrespective of education status. This does not correspond with the findings from 5 rounds of syphilis surveillance among pregnant women in Zambia between 1994–2008 which showed consistently lower risk of syphilis in higher educated women [28]. It is likely that GUD is substantially under-reported in this population-based survey, and therefore this lack of association could be explained by differential reporting bias, i.e. that under-reporting is negatively associated with level of education due to a higher level of awareness among the higher educated. Under-reporting could also be due to both recall and social desirability biases, and may result in no apparent associations, especially for small samples and rare conditions, as in this case.

In this study, the majority of the respondents from the general population sought care from a public health facility, but 40% sought care from private or “other” unspecified facilities. “Other” facilities comprised of a shop or pharmacy and the non-biomedical sector. Alternative sources for STI care reported previously in Zambia and other African countries include chemists/pharmacies and traditional healers [18,19,29,30]. Reasons cited in literature, why patients seek care outside the public sector, include long waiting time at the health facilities, lack of privacy, lack of drugs and insistence on bringing the sexual partner(s) for treatment [18,19,31,32]. Although the quality of services varies in both private and public health facilities, there are reports that suggest that the latter provide better STI services [17,33-35]. Public facilities may be better placed in providing good services if a functional national STI programme is in existence, which involves in-service trainings, provision of treatment guidelines and ensuring constant drug supplies for syndromic management of STIs. Literature shows that many private facilities fall short of standardised care [34] as seen in a South African study in Hlabisa, which compared STI therapeutic practices of private doctors with standard guidelines from the provincial health department. The treatment of STIs by the private doctors was not in line with provincial guidelines. In that study, patients were inadequately treated and a variation was observed in the type of treatment prescribed for any single syndrome among the doctors [36]. In Zambia, periodic performance appraisals are conducted for all public facilities by supervising authorities. Public facilities also benefit from capacity building programmes organised by the national control programme, while private facilities are often not included in these quality assurance mechanisms. Considering the different players involved in care for STIs, standardised STI care in both public and private facilities should be an important strategy in reducing STI morbidity. Another key strategy is to increase awareness among the traditional healers on STIs, their consequences, and the need to refer patients to health facilities where effective treatment can be obtained. Encouragingly, only a minority of the patients from the GUD study in Lusaka sought care >2weeks after symptom onset. It was however surprising that the DHS data showed that there were only minor differences in care seeking by residence and socioeconomic position indicators. Considering that only 50% of the rural population in Zambia live within 5km of a health facility, compared to >90% of the urban population, one would have expected a difference in the likelihood of seeking care between urban and rural residents [37]. The data suggest that there are no substantial inequities to care seeking in this setting. This finding should be interpreted with caution since the association might be affected by the likely substantial under-reporting of symptoms.

In the GUD study, almost half the patients had partners who were aware of their STI. The association found between partner awareness and higher likelihood of engaging in sex after onset of symptoms may indicate that the ulcer had become visible during intercourse. However, it is surprising that only 16% of those who had partners who were aware of the ulcer used condoms consistently. Condom use in Africa is still generally low [34,38] and having sex while having symptoms of an STI also seem to be common as seen in other studies too [30,39,40]. These findings indicate that partner notification may only stop transmission if the partner is successfully treated, since awareness of an ulcer may not result in preventive precautions. Partner notification and treatment, and patient counselling and advice to inform their partners to seek care are all included in the Zambian STI guidelines. However, there is no legal framework-backing for this, and the notification system does not function optimally [41]. Although notification and referral to facilities for treatment may deter some patients from seeking care at government facilities [19], it remains important for reducing secondary spread and re-infections. However, patients` unwillingness to disclose all partners, can impede such notification programmes, and tracing partners without the assistance of the source patient is time-consuming [41]. Of concern was also the high proportion of GUD patients who did not know their HIV status, considering the increased risk of such patients to acquire or transmit HIV to their partners. This is compounded by low condom use and tendency to continue having unprotected sex while symptomatic. Control programmes must attempt to ensure that most GUD patients are tested for HIV and risk reduction messages are re-enforced.