HIV/AIDS, by Mode of Exposure

The proportions of cases attributed to specific exposure (i.e., risk) categories have changed significantly in recent years. Throughout the epidemic, most HIV transmission has occurred among MSM; however, the proportion of cases attributed to male-male sexual activity has been declining. The proportion of cases among persons who report specific heterosexual contact with a person with, or at increased risk for, HIV infection (e.g., an IDU) has been increasing, in large part due to the increase in the proportion of cases among women (data not shown). In 2001, the numbers of new HIV cases in MSM and in heterosexual adults were similar (Figure 9).

Figure 9: Trends in Exposure Categories of Cases of HIV/AIDS, Louisiana, 1997-2001

After adjustment for unreported risk, the largest proportion of cases diagnosed in 2001 (38%) was attributed to heterosexual contact (Table 11). Cases among MSM, including MSM who inject drugs, accounted for 37% of all cases diagnosed in 2001; however, nearly half of all persons living with HIV in Louisiana (48%) may have been exposed to the virus through male-male sexual contact. IDUs constitute an important risk group as well, accounting for 22% of newly diagnosed cases and 23% of persons living with HIV/AIDS.

Among both blacks and whites, the number of new cases diagnosed among MSM has declined during recent years (Figures 10 and 11); however, this decline is more pronounced among whites. Among blacks, heterosexual contact has emerged as the leading exposure category, accounting for nearly half of all newly diagnosed cases (44%) (Table 12). Among whites, the predominant exposure remains male-to-male sexual activity (total of 62%, male-to-male sexual activity and male-to-male sexual activity plus injection drug use) (Table 12), although the number of new cases among MSM has been declining.

Figure 10: Trends in Exposure Categories of Cases of HIV/AIDS in Black Adults
Louisiana, 1997-2001

Note: Number of cases adjusted for risk distribution.
Male-to-male sex includes MSM who inject drugs.

Figure 11: Trends in Exposure Categories of Cases of HIV/AIDS in White Adults
Louisiana, 1997-2001

Note: Number of cases adjusted for risk distribution.
Male-to-male sex includes MSM who inject drugs.

In 2001, 74% of new cases diagnosed among women were attributed to heterosexual contact, and 23% were attributed to injection drug use (Table 13). Among men, more than half of the new cases occurred in MSM (58%, including MSM who inject drugs). Injection drug use was the second most commonly reported risk among men, accounting for 22% of cases diagnosed among men in 2001.

Perinatal transmission dropped dramatically from 1993 to 1997 with the introduction and widespread use of antiretroviral therapy during pregnancy and labor and delivery (Figure 12). In recent years, the perinatal transmission rates have remained fairly stable. Since 1996, the number of infants born to HIV-infected mothers has also leveled. Despite the stable transmission rates, the number of HIV-infected infants may increase as the number of infants born to HIV-infected mothers increases because growing numbers of women are living with HIV infection. Of the 175 infants born in 2000 to HIV-infected mothers, 9 have a diagnosis of HIV infection. Note: For additional information regarding risk for perinatal HIV exposure, see pp. 82-83, Enhanced Perinatal Surveillance.

Figure 12: Infants Born to HIV+ Mothers and Perinatal Transmission Rates
Louisiana, 1993-2000

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