RT Journal Article SR Electronic T1 Why is the infectious stage of syphilis prolonged? JF The British Journal of Venereal Diseases JO Br J Vener Dis FD BMJ Publishing Group Ltd SP 45 OP 49 DO 10.1136/sti.50.1.45 VO 50 IS 1 A1 D J Wright A1 A S Grimble YR 1974 UL http://sti.bmj.com/content/50/1/45.abstract AB