HIV incidence in the United States, 1978-1999.
BACKGROUND
HIV incidence measurements, which reflect recent or current transmission, are valuable for monitoring the epidemic and evaluating prevention programs.


OBJECTIVE
To summarize HIV incidence patterns and trends in U.S. population groups.


METHODS
Publications in English from 1980 through mid-2000. STUDY SELECTION AND STATISTICAL METHODS: We searched the literature for reports of HIV incidence in the United States. Locally weighted scatterplot smoothing was used to generate smooth curves to estimate trends in incidence. Spearman rank correlation was used to estimate the correlation coefficient between prevalence and incidence.


RESULTS
In 74 eligible reports, HIV incidence varied widely (0.002-19.8 per 100 person-years [py]) depending on risk group. Among men who have sex with men (MSM), HIV incidence peaked in the early 1980s (5-20/100 py) and then declined but remained high during the 1990s (2-4/100 py). Among injection drug users (IDUs), incidence decreased since the mid-1980s but differed by geographic area; in the 1990s, incidence remained high in the East (1-3/100 py) but was lower in the West (<0.5/100 py). Throughout the late 1980s and 1990s, incidence was low and stable in broader populations (blood donors: <0.01/100 py; military personnel: 0.01-0.07/100 py). The correlation between HIV incidence and prevalence was strong in populations with a prevalence less than 1% (r = 0.94, p<.0001), moderate in populations with a prevalence from 1% to less than 10% (r = 0.57, p<.0001), and weak in populations with a prevalence at least 10% (r = 0.23, p=.09).


CONCLUSIONS
HIV prevention in the United States should continue to focus on MSM and IDUs. HIV incidence measurements should be considered for monitoring HIV transmission in MSM, IDUs, and other populations in which seroprevalence is high.
Vu
Minh Quan
MQ
Division of HIV/AIDS Prevention, National Centre for HIV, STD, and TB Prevention, Epidemic Intelligence Service, Epidemiology Program Office, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. VQuan@cdc.gov
Steketee
Richard W
RW
Valleroy
Linda
L
Weinstock
Hillard
H
Karon
John
J
Janssen
Robert
R
D000293:Adolescent; D000328:Adult; D001782:Blood Donors; D005260:Female; D015658:HIV Infections / Q000453:epidemiology* / Q000517:prevention & control; D018451:Homosexuality, Male; D006801:Humans; D015994:Incidence; D008297:Male; D008889:Military Personnel; D011159:Population Surveillance; D015995:Prevalence; D012307:Risk Factors; D015819:Substance Abuse, Intravenous; D014481:United States / Q000453:epidemiology