Cases of HIV type 1 acute infection at STI-related clinics in Osaka

Since 1992 we have investigated HIV antibodies in persons with a venereal disease who worked for a sex business or engaged in sexual behavior with a high risk of HIV infection at five clinics of venereology, urology, and gynecology in Osaka Prefecture. Starting at the end of 2000, we performed a nucleic acid-amplification test (NAT) on antibody-negative samples with the aim of detecting cases in the window period covering the early phase of infection. Three cases that were thought to be in this phase were found in 2006. All were confirmed to be positive in an NAT, although they were negative in initial screening for HIV performed using the IC method. Gene analysis of the env-C2V3 region of HIV-1 showed that the three samples had different origins.