HIV type 2 in New York City, 2000-2008.

Background. Antibody cross-reactivity complicates differential diagnosis of human immunodeficiency virus (HIV) type 2 (HIV-2) using standard serologic screening and confirmatory tests for HIV. HIV type 1 (HIV-1) viral load testing does not detect HIV-2. Although HIV-2 is, in general, less pathogenic than HIV-1, it can lead to immunosuppression and clinical AIDS, and there are important differences in the selection of antiretroviral therapy for HIV-2-related immunosuppression that make it imperative to differentiate between the 2 viruses. The New York City Department of Health (New York, NY) seeks to facilitate accurate diagnosis and surveillance of HIV-2 infection in the city. Methods. We used routine HIV-1-2+O screening and a comprehensive algorithm to differentiate between HIV-1 and HIV-2 infection, universal HIV-related laboratory test reporting, population-based surveillance of HIV infection, and active communication with clinicians. Results. Between 1 June 2000 and 31 December 2008, 62 persons received a diagnosis of confirmed or probable HIV-2 infection. The majority (60 [96.8%] of 62 individuals) were foreign-born (96.7% were born in Africa) and of black race/ethnicity (93.5%). At the time of initial diagnosis, 17.7% of patients with HIV-2 infection had AIDS. Forty (64.5%) of the patients received an initial diagnosis of HIV-1 infection. Among these patients, the median lag between initial diagnosis of HIV-1 infection and identification of HIV-2 as the infecting organism was 487.5 days. Conclusion. HIV-2 should be ruled out in persons presenting for HIV testing who originate in or travel to West Africa and other areas in which HIV-2 is endemic, particularly those who have negative or indeterminate results on HIV-1 Western blot testing or have atypical banding patterns and/or present with clinical signs of HIV infection or unexplained immunosuppression.