Study finds further evidence Mycoplasma genitalium, which has few symptoms, is sexually transmitted and may be present in 1% of adults under 45

A sexually transmitted infection could have infected hundreds of thousands of people in the UK, research suggests.

Mycoplasma genitalium, known as MG, has very few symptoms but is now known to be passed on through sex. It is estimated to affect 1% of 16- to 44-year-olds who report having had at least one sexual partner.

MG has previously been identified as causing discharge; testicular pain, pelvic pain and bleeding after sex in women, although most people have no symptoms at all.

Scientists believe MG plays a role in pelvic inflammatory disease, infertility and ectopic pregnancy. The existence of the bacterium was first reported in the early 1980s.

Nigel Field, consultant clinical epidemiologist at Public Health England (PHE), which worked on the study, said it had found further evidence that MG is an STI.

“MG is a bacterium that was present in around 1% of the general population aged 16 to 44 years, who had reported at least one sexual partner,” he said. “The study adds to the accumulating evidence base that MG causes infection in some men and women, and the study found that women with MG were more likely to report bleeding after sexual activity. “However, over 90% of men and more than half of women with MG had no symptoms. It may be that MG does not cause illness in all individuals in whom the infection is detected. Laboratory testing for MG is not yet widely available in the UK.”

He said further research into the clinical consequences of MG infection were needed before work could begin on possible screening or steps to prevent it.

Field added: “PHE has recently established national surveillance to monitor diagnoses of MG from any clinics undertaking testing and will continue to gather public health data on MG to inform policy on infection control.

“As for all STIs, prevention measures promoting increased condom use and a reduction in sexual risk behaviours are likely to play an important role in efforts to control MG.”

The study, which was published in the International Journal of Epidemiology, found the rate of infection was much higher in those who reported more than four sexual partners in the past year.

The majority of participants who tested positive for MG did not report any symptoms in the last month.

More than half of women did not report any symptoms, but among those who did, bleeding after sex was found to be the most common.

Pam Sonnenberg, lead author of the paper, said: “These findings suggest that only testing those who are currently symptomatic would miss the majority of infections. However, further research is needed to understand the clinical implications of infection and possible longer term complications.”