HIV Incidence Surveillance in Philadelphia

Background: HIV Incidence Surveillance (HIS) was implemented in Philadelphia as of July 2005 as part of a 34 site, nationwide effort to improve HIV incidence estimates. The Serological Testing Algorithm for Recent HIV Seroconversion (STARHS) estimates infection rates within one year (‘recent') or greater than one year (‘long-term'). We used remnant serum samples from confirmatory Western Blots and viral load assays to do STARHS testing and estimate HIV incidence.

Methods: Data was used from newly diagnosed, confidential name-based HIV/AIDS cases reported in Philadelphia from January 2006. STARHS testing was performed on blood samples from eligible cases; results were analyzed for their association with race/ethnicity, sex, infection mode, age at diagnosis, and concurrent HIV and AIDS diagnoses.

Results: To date, there are 912 HIS eligible cases; 720 have been fully investigated and 299 have undergone STARHS testing. Of those tested, 22.4% are ‘recent' infections (n=67), which was comprised of 50.8% females and 64.2% African Americans. Heterosexual contact was the mode of transmission for 67.2 % of ‘recent' and 62.1% of ‘long-term' infections. Thirty-four percent of ‘recent' infections were 30-39 year-olds; not a significant difference from 40-49 year-olds (24%) or 20-29 year-olds (22.4%). Concurrent HIV and AIDS diagnoses occurred in 44% of ‘long-term' infections (n=232).

Conclusions: Both ‘recent' and ‘long-term' HIV/AIDS cases in Philadelphia were predominantly infected through heterosexual contact and are African Americans. The high incidence of ‘recent' infections and concurrent HIV and AIDS diagnoses support the need to implement the CDC's recommendations for increased HIV screening and early intervention.