And that question has been answered. Use a condom (correctly), and use legitimate prostitutes preferably Dutch. All sexual contacts, paid or not, cary the risks of STD. Nobody here is going to tell you that sex is 100% safe, because it never is!
And what about East European girls, are they considered safe aswell ? There are quite a few Romanian and Hungarian girls too in the Business.
Any place has people who are prone to diseases. So it is better to avoid having sex with unknown people. Though prostitution is legal in certain countries, it is better to have safe sex.