Mycoplasma genitalium, known as MG, affects between 1% and 2% of the population, according to the British Association of Sexual Health and HIV (BASHH).
But tests to diagnose it are not routinely available, and BASHH have described the spread of the disease as a “public health emergency waiting to happen”.
MG can cause no symptoms and is often misdiagnosed as a different disease such as chlamydia.
But medicines for chlamydia are ineffective for MG, leading medical professionals to warn that the infection could become resistant to antibiotics and untreatable within a decade if steps are not taken to tackle it.
Data from Public Health England shows that 2,461 people in Sheffield were diagnosed with chlamydia last year alone. But this accounts for just 0.4% of the adults in the area, meaning many cases of MG or chlamydia are likely to be undiagnosed.
Just 19% of adults aged between 15 and 24, among whom chlamydia is most easily spread, were screened for chlamydia in 2017.
New guidelines on how to tackle MG have been accredited this month by the National Institute for Health and Care Excellence.
But seven in every 10 sexual health experts across the country said they were not able to afford the diagnostic tests recommended by the guidelines, BASHH said, leading to concerns the disease will be mistreated and become resistant to antibiotics.
If this happens, the organisation says that up to 3,000 women a year nationally who have pelvic inflammatory disease (PID) caused by MG could be at risk of infertility.
BASHH’s Paddy Horner said: “MG is treated with antibiotics, but as until recently there has been no commercially available test, it has often been misdiagnosed as chlamydia and treated as such.
"This is not curing the infection and is causing antimicrobial resistance in MG patients. If practices do not change and the tests are not used, MG has the potential to become a superbug within a decade, resistant to standard antibiotics.
"The greatest consequence of this is for the women who present with PID caused by MG, which would be very hard to treat, putting them at increased risk of infertility.
"These new guidelines have been developed because we can’t afford to continue with the approach we have followed for the past 15 years, as this will undoubtedly lead to a public health emergency with the emergence of MG as a superbug."
The new recommended guidelines propose the introduction of an accurate MG test and effective treatment for the infection.
BASHH have also called on the government to make more funding available to sexual health clinics to tackle the disease.
The new guidelines come two months after a British man was reported to have the “world’s worst” case of super-gonorrhoea. Like MG, it also proved resistant to antibiotics.
MG is lower profile then gonorrhoea, but more widespread. Last year, in Sheffield, 334 people were diagnosed with gonorrhoea.