Background:
Syphilis is a sexually transmitted disease (STD) that increases the likelihood of sexual HIV transmission 2-5 times. Risk factors for both infections include vaginal intercourse, oral sex or anal sex without protection or parenteral transmission.

Objective:
Describe the occurrence and distribution of syphilis and HIV infections by age and gender for the period 2004-2006 in Puerto Rico. Define the distribution of risk factors among syphilis cases and the occurrence of syphilis and HIV co-infections.

Method:
Data from the US Census Bureau and Puerto Rico STD Surveillance Office was used to describe the demographic characteristics, occurrence of co-infection, risk factors and to calculate the incidence rate of Syphilis in Puerto Rico from 2004-2006.

Result:
For the period of 2004-2006
- A total of 212 people with syphilis were reported to have a positive HIV test either previous or current.
- The 60.1% of the cases were men.
- The highest incidence of co-infection was shown for the 20 to 39 years age group
- The most important risk factors were Heterosexual sex (average 51%), Men sex with men (MSM) (average 33.4%), Use of injecting drugs (average 8.3%) and Sex for drugs or money (average 5.2%).

Conclusion:
Unprotected sex is still a huge problem in the control of syphilis particularly in the “MSM” population. Awareness of HIV status does not seem to be a precursor for safer sexual practices.

Implications:
Design the STD and HIV prevention campaigns require age, gender and cultural considerations. Maintain the surveillance system is important to analyze the trends of these infections.