BACKCALCULATION OF THE NUMBER INFECTED WITH HUMAN-IMMUNODEFICIENCY-VIRUS IN GERMANY

The method of backcalculation was used to estimate the cumulative numb er of human immunodeficiency virus type 1 (HIV-1)-infected adults in G ermany from reporting delay-corrected surveillance data on acquired im munodeficiency syndrome (AIDS) in the pretreatment era. Using differen t backcalculation approaches with various incubation period distributi ons, a plausible range of 13,100 to 23,900 HIV-1-infected adults as of December 31, 1984, was calculated. Estimates of the number infected a t more recent times were subject to much greater uncertainty. On avera ge, the cumulative incidences calculated by the nonparametric backproj ection method are about 15% lower than the results from the step funct ion model. Nonparametric backprojection with the Hessol incubation dis tribution suggests a declining HIV infection rate after 1985, as might be expected from German health policies. This distribution is derived from cohorts of homosexual men, the main fraction of German AIDS case s.