I suspect it's both. I know people who work in the sex industry (yeah, nah.) and they reckon Tinder hookups are a pretty good way to get the clap. Given the article above I would be curious to see the rates from other locations where African immigration isn't as high.
And some reading:
https://www.itg.be/E/Article/syphilis-almost-eliminated-almost-everywhere-except-in-africa
This one has maps.
https://www.independent.co.uk/news/science/syphilis-map-stis-stds-world-global-rates-disease-a7024511.html
Looks like the brilliant government is importing more than 457 workers.....
