REDEFINING THE GROWTH OF THE HETEROSEXUAL HIV AIDS EPIDEMIC IN CHICAGO/

A dramatic shift in the relative distribution of the five categories o f heterosexual transmission for AIDS cases diagnosed in Chicago since 1991 prompted a mode-of-transmission validation study of what had beco me the most frequently reported heterosexual exposure: heterosexual re lations with a person with AIDS (PWA) or documented HIV infection whos e risk is not specified. Methods: For 395 cases with originally report ed heterosexual exposure, one or more of three supplemental data sourc es were employed: medical records were reviewed, medical providers wer e interviewed, and patients or proxies (i.e., spouse, significant othe r, or family member) were interviewed when possible. When reported HIV exposure could not be validated or reclassified, the transmission cat egory employed was ''no identifiable risk'' (NIR). Results: Eighty-fiv e percent (336 of 395 cases) were reclassified into different transmis sion categories. Most notably, 69% (272 of 395 cases) were reclassifie d into transmission categories that did not involve heterosexual conta ct, including NIR. The cumulative percentage of cases attributable to heterosexual contact declined from 8% to 5% as a result of reclassific ation. Additionally, reclassification resulted in a reduction of nearl y 50% in the number of AIDS cases attributable to heterosexual contact diagnosed in 1993 and 1994. Conclusions: In Chicago, an emerging prob lem in AIDS surveillance appears to be the use of an ambiguous heteros exual exposure category as a default when other information is not rea dily available. This study has found the growth in AIDS cases among pe rsons exposed to HIV through heterosexual contact to be much slower th an previously perceived. This finding may have important implications for the national debate over the extent to which heterosexual people a re being infected and how funding and prevention strategies should be prioritized.