Introduction

Sexually transmitted diseases represent a major public health problem and the advent of HIV infection during the past decade has highlighted the importance of infections spread by the sexual route.

The purpose of this study was to report trends of gonorrhoea and early syphilis in the Belgrade population (about two million inhabitants) during the period 1985–99, and to discuss the data in the light of changes in gonorrhoea and syphilis rates in other countries of eastern Europe.

Material and methods

Primary, secondary, and early latent syphilis (referred to as early syphilis) were defined using generally accepted criteria. For diagnosis of early syphilis the Venereal Disease Research Laboratory (VDRL) and Treponema pallidum haemagglutination (TPHA) tests were used. For diagnosis of gonorrhoea standard laboratory examination was used—that is, microscopy and inoculation on culture media. Reporting on syphilis and gonorrhoea is compulsory in Yugoslavia. In Belgrade all reports are sent to the municipal department for skin and venereal diseases. These reports were used as the source of data for incidence cases.

The incidence rates for syphilis and gonorrhoea were calculated using data from the 1991 Yugoslav census for the Belgrade population. Age adjustment of yearly incidence was carried out by a direct method using the “World population” as the standard.

Data about possible source of infection, provided on the official form for notification of syphilis and gonorrhoea, were also analysed.

Results

The early syphilis incidence rates in men showed a decreasing trend during the first half of the period observed, followed by an increase beginning from the year 1993 (y = 4.74 − 0.84x + 0.06x², p = 0.018) (table 1 and fig 1). In women these variations in incidence were less pronounced. During the period observed, only mild increase of syphilis incidence was recorded among them (y = 0.69 + 0.05x, p = 0.032). The disease was more common in men, the male/female ratio ranging from 0.8 to 6.6.

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Figure 1

Incidence of early syphilis (per 100 000)* and incidence of gonorrhoea (per 100 000)* by sex in Belgrade 1985–99

Gonorrhoea incidence had significant decreasing trend in both men and women (y = 112.73 − 7.73x, p = 0.000, and y = 39.54 − 2.86x, p = 0.000 respectively) (table 1). During the period 1985–99, gonorrhoea incidence decreased by 90.8% among men, from 140.08 per 100 000 in 1985 to 12.94 per 100 000 in 1999, and by 93.9% among women, from 48.39 to 2.96 per 100 000. Between 1992 and 1993 gonorrhoea incidence increased by 14.8% in men and by 51.7% in women. In all years observed the disease was more common in men. The male/female ratio ranged from 2.5 to 4.8.

The incidence of syphilis in Belgrade was highest in men aged 30–39 and 40–49 and in women 30–39 and 20–29 years old. The incidence of gonorrhoea was highest in men and women 20–29 years old. In both sexes the lowest incidence rates for syphilis and gonorrhoea were in children below 15 years of age and in people aged 50 years or more. Incidence rates were higher among males than among females, and the male/female ratio increased with age, up to 50 years of age.

Most frequently, male gonorrhoea cases did not indicate possible source of infection, but for most of the female cases the source of infection was their regular sexual partner. However, over 80% of male syphilis cases reported sexual intercourse in Russia or Ukraine as the probable source of infection, where they had found temporary employment after suspension of UN sanctions in 1995. Later they transmitted syphilis to their sexual partners in Belgrade (all women were infected by their regular sexual partners). The remaining of male syphilis cases most frequently indicated sexual intercourse with a casual acquaintance in Belgrade as the possible source of infection.

Discussion

The most plausible explanation for the gradually decreasing trend of early syphilis and gonorrhoea incidence rates in men during the period 1985–92 lies in the changes in sexual behaviour in response to the AIDS epidemic. According to the literature data the common factor underlying the falling incidence of syphilis, gonorrhoea, and other sexually transmitted diseases, especially among homosexuals, has been concern over AIDS through its deterrent effect on high risk sexual behaviour.

The increase of gonorrhoea incidence in the Belgrade population in the years 1993 and 1994 could be explained by adverse changes in the country caused by the war, the break up of the former Yugoslavia, economic sanctions imposed on Serbia and Montenegro by the United Nations, and the resulting socioeconomic difficulties which culminated in 1993. However, the importation of syphilis from countries of the former Soviet Union played a major part in the increase of syphilis incidence.

An alarming increase in syphilis incidence has been recently observed in many eastern European countries. For example, in Romania¹ syphilis incidence has risen steadily from 7.1 cases per 100 000 people in 1986 to 19.8 cases per 100 000 in 1989, and to 34.7 cases per 100 000 in 1998. In Bulgaria syphilis incidence also increased from 14.4 per 100 000 in 1994 to 27.3 per 100 000 in 1996. In Burgas and Vidin (Bulgaria), in the year 1996, the syphilis incidence was 52.8 and 59.8 per 100 000.² This trend was explained by economic crisis and migration. A similar increase was observed in Estonia.³ In Nizhni Novgorod (the city in central Russia with 1.4 million inhabitants), the incidence of syphilis increased from 3.2 cases per 100 000 people in 1990 to 300 cases per 100 000 people in 1997.⁴ According to Karieva and Umanov⁵ low education, poor socioeconomic conditions, and migration were the main causes of increased syphilis incidence in Uzbekistan.

A higher frequency of syphilis and gonorrhoea in men than in women in Belgrade can be explained by differences in their sexual behaviour and by sex differences in the clinical manifestation of the disease (especially gonorrhoea). Men have a more pronounced tendency to change their sexual partners and consequently their exposure to disease is increased.⁶

In the present study the highest incidence of syphilis among men was established in the age group 30–49, and among women in the age group 20–39. Saluvere and Konno³ reported that women aged 20–29 and men aged 30–39 were most commonly infected, because they are sexually more active and more promiscuous than other age groups. The association of young age (in Belgrade population 20–29 years old) with higher gonorrhoea rates is probably due both to age related sexual behaviour and the biological characteristics of the host-pathogen interaction. The higher age of men with the highest incidence of syphilis in our population in comparison with the age of men with the highest incidence of gonorrhoea can be explained by the fact that experienced people went to work in the countries of the former Soviet Union and that the vast majority of syphilis cases were contracted in those countries. Consequently women, their partners in Belgrade, who contracted the disease from them, were on average also older than women who contracted gonorrhoea.

The critical feature of this analysis is the accuracy of data. It is reasonable to assume that the incidence of both diseases, especially gonorrhoea, is underestimated. Some of the patients do not visit physicians, and some physicians do not report all of the cases.