CD4 and syphilis: Incidence of syphilis was particularly high among young patients (age <33 years: 60.1 per 1,000 person-year, 33–40 years: 54.2 per 1,000 person-year, >40 years: 18.8 per 1,000 person-year), those who were incarcerated due to illicit drug use (106.6 per 1,000 person-year), those with history of syphilis at baseline (86.6 per 1,000 person-year), and those with high baseline CD4 count (CD4 ≥350 /μL: 59.6 per 1,000 person-year, 200–349 /μL: 50.7 per 1,000 person-year, <200 /μL: 29.4 per 1,000 person-year) (Table 2).