Pourquoi la syphilis est-elle en augmentation ?

Syphilis has long been considered a 'historical' disease of little relevance in the 21^e century. It was, in effect, eradicated in the UK during the mid-80s and is still relatively uncommon, making up less than 2% of the sexually transmitted infections (STIs) diagnosed in 2017. However, cases have doubled over the past decade and the infection is prevalent in particular communities, with London being more greatly affected than any other region.

Syphilis - cause and effect

Syphilis is caused by the bacterium Treponema pallidum. It is highly contagious and passed on through direct contact with a syphilis sore (ulcer) - typically during vaginal, anal or oral sex with an infected person; the infection is also transmittable via the bloodstream so shared intravenous drug use and unscreened blood products also pose a risk.

Syphilis progresses through a number of stages. The primary phase occurs between 10 days and three months after initial infection, and usually causes a painless ulcer on the genitals or mouth which heals up by itself. A few weeks later, if the initial ulcer isn't treated, the signs of secondary syphilis appear.

Common symptoms may include a widespread rash (which often affects the palms of the hands and the soles of the feet), swollen lymph glands, sore throat, flu-like symptoms, aching muscles and joints and fever. These symptoms can come and go for up to two years. After this period, a person with syphilis is no longer considered to be contagious.

During the third 'latent' stage, there may be no symptoms for many years. Some people will remain in good general health, but for a proportion, the disease will progress to the tertiary phase and may cause significant damage to the heart, brain, nervous system, skin and bones; this can be debilitating and even life-threatening.

According to research by Public Health England (PHE), the recent increase in syphilis has been most significant among men from gay and bisexual communities.

"The PHE report shows that men who have sex with men account for 78% of the syphilis diagnoses in the UK," says Debbie Laycock, head of policy at the Terrence Higgins Trust. "Sexual behaviour is changing, and people are more likely to have more partners and use condoms less often."

"It may also be linked to group sex facilitated by location-sharing apps and 'chemsex'," adds Dr Gwenda Hughes, consultant scientist and head of the STI section at PHE.

The term 'chem sex' refers to sexual activity while under the influence of recreational drugs, which can cloud judgement and make risky sexual behaviour more likely.

"We also know that not all gay men are testing at the frequency we would recommend," says Laycock. "If you have new partners or change partners frequently we would recommend testing for STIs and HIV at least every three months. Not everyone who needs to test regularly does so."

The government has faced criticism from charities and clinicians for reducing spending on NHS sexual health services, which some say is contributing to an increased prevalence of syphilis and other STIs.

"Often sexual health services are too far away, not open at convenient times or too busy for people to access when they need to," continues Laycock. "Recent cuts in funding for sexual health services risk exacerbating the problem by making it even harder for people to access the services they need."

However, PHE is keen to counter this view.

"Overall, we have seen an increase nationally in the number of attendances at sexual health clinics and the number of screens since 2013, which suggests that people are still able to access services," comments Hughes. "There have been small declines in testing in some regions of the country and we would encourage local authorities and service commissioners to investigate the impact of these changes."

As syphilis can have a long latent period - and initial symptoms may be mild or mistaken for other less serious health issues - it is not uncommon for those infected to pass on the disease without realising they are infectious.

Comprehensive sexual health education is key across all communities, to change behaviours and reduce transmission.

"Firstly we need to ensure that every young person gets appropriate LGBT-inclusive relationships and sex education (RSE) at school, so they become aware of how to have a healthy sex life," says Laycock. "It's vital to also invest in effective public health campaigns that continue to educate gay men about STIs, how to prevent them and where to go to get tested and treated. And to invest in good sexual health services which are easy to access and provide testing with a rapid turnaround of results."

According to Hughes, PHE is working closely with stakeholder organisations to reduce syphilis diagnoses across the country, particularly in the men who have sex with men community.

"There has also been a more modest rise in diagnoses among heterosexuals," says Hughes, "which we are investigating to determine whether additional interventions in this population are needed."

If you think you may have syphilis it is crucial to get tested by your GP, or at your local sexual health clinic. Symptoms may mimic those of other health conditions, which can be confusing.

"The symptoms can sometimes be similar to those of other STIs," says Laycock. "Herpes can also cause genital ulcers and the symptoms of early HIV infection (HIV seroconversion) are the same as secondary syphilis."

The infection can usually be easily treated and cured with antibiotics, but the emergence of antibiotic-resistant strains is a concern and makes prevention all the more important. Once you have been diagnosed, it is important to attend the clinic for repeat blood tests after treatment to check the infection has cleared.

"Having had syphilis once does not mean you can't catch it again, so practising safe sex and having regular check-ups remains important," adds Laycock.