Numbers of cases of sexually transmitted infection in the Netherlands have increased by two thirds in three years, leaving researchers “alarmed” because it points to an increase in unsafe sex. The total figure for all sexually transmitted infections rose over three years from about 5500 to 9500.

The researchers' report highlights worrying evidence of people becoming infected both with HIV and other diseases, in particular syphilis, so allowing HIV to be transmitted more easily.

Although the incidence of syphilis is rising in other European countries, the Dutch data show a sharp rise of 78% in 12 months—including a “remarkable” rise of 182% among gay and …