Gonorrhoea is equally common and while easier to suspect and therefore diagnose, is becoming increasingly difficult to treat due to drug resistance. Chlamydia is harder than gonorrhoea to diagnose and treat. Venereal warts are probably three times as common and their key consequence, cervical cancer, is more severe. Chancre is endemic in many developing countries, particularly in SE Asia, eastern and Southern Africa, and Papua New Guinea, and is as unpleasant as it sounds. Prostitutes play an important role in its spread.
Most genital ulcers are due to chancroid, though mixed infections are common.
Viral infections principally affecting the liver, are among the STDs with the highest incidence world-wide. Fortunately, HBV is the first hepatitis virus against which a vaccine has been developed, and indeed the first sexually transmitted disease against which there is an effective vaccine. Recently, preliminary evidence has been forthcoming to suggest that a hitherto - unsuspected route of transmission, viz via bed bugs, may be important. Hepatitis C virus is also transmitted by sexual contact. Sexual transmission of HIV accounts for about three quarters of all infections world-wide.