Rural communities where people have less access to healthcare and more conservative attitudes towards sex may be fuelling a rise in syphilis, experts warn.
More than 101,000 people in the US were diagnosed with syphilis in 2017 and officials have raised concerns about a resurgence in the UK and Australia, too.
Figures have suggested the use of heroin and methamphetamine are driving up syphilis rates in the US, but where people live may also be a factor.
In small towns people might be afraid of seeing a doctor they know personally, or doctors who have never seen syphilis before may struggle to diagnose it, experts suggest.
The state of Louisiana was worst affected by syphilis in 2017, followed by Nevada and California. The least affected areas were Wyoming and Alaska
Karolyn Schrage, director of a medical clinic in Joplin, Missouri, said she saw 32 cases of syphilis in the first quarter of this year, up from just five in early 2018.
'I've not seen anything like it in my history of doing sexual health care,' she told Kaiser Health News.
'It really is astounding to me that in the modern Western world we are dealing with the epidemic that was almost eradicated,' she added.
In the state as a whole, the number of syphilis cases has risen from 425 in 2012 to 1,896 in 2018.
A disproportionate amount – almost half – are happening outside of the cities of Kansas City and St Louis, in more rural areas.
Experts believe this could be because people in the country have less access to healthcare, less knowledge of sexually transmitted diseases, and potentially more conservative opinions on sex outside of marriage or gay sex, KHN reports.
And, in small towns, people's embarrassment may be made worse by having to see a doctor who is also their Sunday school teacher or knows members of their family.
Syphilis is a bacterial infection that is usually caught by having sex with an infected person.
It spreads through close contact with an infected sore, which usually happens during vaginal, oral or anal sex.
Infected pregnant
