The increase appears to be the result of a combination of factors, including changes in sexual behavior, in immigration patterns and in the microorganisms themselves.

Although the epidemiological statistics may seem alarming, new techniques in molecular biology and genetics discussed in Istanbul should facilitate screening and prevention of sexually transmitted infections.

Adolescents and young adults, as the most vulnerable group, are the major target of STD prevention programs. However, few epidemiological studies have been carried out among the age group in question, largely because young people are notoriously difficult to follow up over a long period.

So the unpublished prospective study presented to the ECCMID Congress by a team from Bologna University was of particular interest to participants. Its goal was to examine the incidence of STDs among young people in a large Italian city, the origin of the infection, and the group's risk factors.

The time frame of the study was 1991 to 1999, during which period 284 adolescents and young adults between the ages of 13 and 20 sought medical assistance for a sexually transmitted disease.

The study shows that adolescents are at significant risk of contracting an STD. On average, over 6% of the 4,646 first-time STD patients seen were between the ages of 13 and 20.

There was a very broad range of infections: non-gonococcal STDs were the leaders, representing 34% of cases, while herpes accounted for another 26% and a further 6.1 to 7.4% of cases were identified as chlamydia, molluscum or gonorrhea. There were even 13 young people with two STDs.

While the average age of patients remained virtually static at 19 throughout the study, the proportion of youngsters seeking treatment for an STD almost tripled over the nine-year period, increasing from 3.6% in 1991 to 13.3% by the end of 1999. Ten per cent of patients were aged under 18.

The number of women carrying STDs had also increased significantly, as Dr. Roberto Manfredi, the study's author, explained. Since 1997, there had been more girls and young women than boys seeking treatment for STDs; in the final year, they represented the overwhelming majority (52 out of a total of 59 patients).

To some extent, that increase could be attributed to the mass arrival, from 1993 onwards, of young foreign prostitutes. (Not all of the clinic's patients were Italian: while, on average, they represented 62% of patients, three-quarters of the young people seen towards the end of the study were foreigners.)

Why the rise? The Bologna team tried to answer this question by pointing not only to the clinical results but also to data on socioeconomic, demographic and behavioral factors.

Their conclusion: if one disregards the prostitutes' influence, the rise in infections is due above all to increasing promiscuity, a failure to use condoms and a low level of education.

"Almost a third of these young people had had between two and nine partners in the last six months and over 23% had even had ten partners or more," explained Manfredi. "Over 70% of our subjects did not use condoms." That proportion was as high as 96% for under-18s, while for prostitutes it was only 10%.

The educational level of the group was relatively low: almost two-thirds had received only elementary education and none of the subjects had been to university.

The conclusion Manfredi presented to ECCMID was quite clear: "This study demonstrates a relative and absolute increase in the number of adolescents carrying STDs, as compared to the over-21 age group. So there is an urgent need to conduct continuous monitoring of STDs in adolescents and young adults if we want to achieve targeted prevention strategies specially adapted to this age group."

Sexually transmitted diseases will also be on the agenda on Wednesday at the ECCMID symposium No. 3, entitled "Typing Methods for Epidemiological Analysis of Infectious Diseases".

Among other things, the symposium will be discussing gonorrhea, one of the world's commonest STDs (there are thought to be over 100 million cases), which has made a remarkable comeback in recent years (+56% in the United Kingdom alone between 1995 and 1999).

Gonorrhea infections, caused by gonococcus (Neisseria gonorrhea), are still poorly controlled. As with all STDs, it is difficult to trace the chain of infection, since sexual partners are often very hard to identify. Yet the only effective way of combating the disease is to treat not only the infected person but also all of his or her partners.

A London team, under Helen Ward and Catherine Ison, of Imperial College School of Medicine, has come up with an original solution to the problem of tracing sexual partners that they are presenting to the 11th ECCMID.

The method is based on a genetic peculiarity of gonococcus: one of its genes (known to specialists as opa) is both variable and relatively well preserved when the disease is passed from one person to another.

It should be possible to use that feature to trace the path of infection from one sexual partner to another.

The researchers put the theory to the test by determining the characteristics of the opa gene in 215 cases of gonorrhea observed during six months of consultation in London and 12 months in Sheffield.

The results were then compared, both with epidemiological data obtained using a questionnaire on each subject's sexual partners during the past three months and with two other methods habitually used to type the bacteria.

The opa method obtained a higher degree of discrimination than the classical methods and showed a strong correlation between "genetic typing" and epidemiological data.

The new method had even allowed identification of a greater number of sexual partners than the questionnaire responses suggested.

Ison also said that many of the London cases had been found to be unconnected, whereas two main strains were found to be responsible for half of the Sheffield infections. She concluded that determination of the opa gene characteristics made it possible to identify an epidemic of sporadic cases.

"Where a single type of opa gene is found, it suggests the existence of a transmission network proper, which is not the case where there are a number of different strains."

The method could also prove to be an excellent way of studying the spread of gonococcus within a population group for epidemiological or legal medical purposes, as is already the case in Great Britain.

[Contact: Roberto Manfredi, Amy Hern, Catherine Ison ]

03-Apr-2001