Reports on HIV/AIDS: 1990

NOVEMBER 30, 1990, MMWR, Vol. 39, RR-16 [inclusive page numbers]
participants used an estimate of the sizes of the various populations at risk and the
estimated HIV seroprevalence in the groups. Since the HIV antibody test had been
licensed only a year earlier, seroprevalence data were limited, and little was known
about the long-term natural history of HIV infection. At the time of the Coolfont
workshop, 21,000 cases of AIDS had been reporteJ to CDC. The Institute of Medicine,
National Academy of Sciences, reviewed and did not challenge the estimate of 1-1.5
million HIV infections (14).
By 1987, more seroprevalence data were available, and the direct estimate of the
number of HIV infections was revised to a slightly lower range of 945,000-1.4 million
(11 ). Estimates from back-calculation included a wider range (420,000-1.65 million).
Current estimates derived from back-calculation. Since 1987, the backcalculation method has been further refined, more information has become available
on the distribution of incubation times, and the change in trends of AIDS incidence
has become apparent. In addition, more extensive seroprevalence data on sentinel
populations are now available from CDC's surveys and studies.
Four workshop participants summarized current estimates of HIV prevalence
based on the back-calculation method and presented analyses for more detailed
discussion (Brookmeyer, Hay, Hyman, and Rosenberg). Additional analyses were
done after the workshop. CDC adjusted all estimates for previous deaths, underreporting of AIDS cases, and deaths due to HIV infection in persons not meeting the
AIDS surveillance definition* (see Appendices A and B).
On the basis of these back-calculation analyses, CDC now estimates that approximately 750,000 persons in the United States were infected with HIV at the beginning
of 1986 (Table 1). Estimates of current HIV prevalence based on these analyses range
from 650,000 to 1.4 million. The median of these estimates is >900,000, and only one
estimate is <850,000. The wide variation among the estimates for recent years
reflects the sensitivity of the back-calculation approach to more recent surveillance
data reports and to varying estimates of the distribution of incubation times.
The group agreed that back-calculation provides a basis for estimating past
HIV-infection prevalence and future AIDS incidence. However, the accuracy of this
method depends on the validity of the necessary assumptions and adjustments
made, especially those concerning the completeness of AIDS case reporting and the
estimated distribution of incubation periods.
Current estimates derived from empirical data. The group also reviewed estimates of total HIV prevalence derived from seroprevalence data from CDC's family of
surveys. Participants evaluated a framework of age- and sex-specific HIV-prevalence
rates derived from data from the sentinel hospital network (15). Prevalence data from
civilian applicants for military service, childbearing women, ambulatory patients, Job
Corps entrants, and federal prisoners were compared with the expected rates, with
consideration given to the probable biases involved. The results of these preliminary
analyses were consistent with prevalence estimates ranging from a minimum of
approximately 300,000 (based on rates from applicants for military service) to a
maximum of approximately 1.5 million (based on rates from federal prisoners).
*CDC estimates that 70%-90% of all HIV-related deaths among men 25-44 years of age (the
group most affected by the HIV/AIDS epidemic) are reported through AIDS surveillance (7) and
that 85% of all diagnosed cases of AIDS (as defined by national surveillance criteria) are reported
(see Appendix A).

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