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HIV-2 Remains Rare in the U.S., Says CDC Report

Fewer than 200 cases meeting the CDC's definition of HIV-2 infection were reported between 1988 and 2010, accounting for only 0.01% of all HIV cases, according to a study described in the July 29, 2011, issue of Morbidity and Mortality Weekly Report. About half these cases were in New York City, mostly among people from West Africa.alt

There are 2 types of human immunodeficiency virus, HIV-1 and HIV-2. Though transmitted by similar routes, HIV-2 causes less aggressive disease with slower deterioration of immune function. HIV-2 is also much less common, mostly occurring in West Africa.

Over the course of the epidemic, the U.S. Centers for Disease Control and Prevention (CDC) HIV surveillance case definition has applied to both types. In 2009, the CDC convened a working group to develop a working case definition to distinguish between HIV-1 and HIV-2.

To meet the definition of HIV-2, cases had to satisfy at least 1 of the following criteria:

  • HIV-1/HIV-2 type-differentiating antibody test (e.g., Bio-Rad Multispot HIV1/HIV-2 Rapid Test) positive for HIV-2 but negative for HIV-1;
  • Positive HIV-2 nucleic acid test (DNA or RNA);
  • Positive HIV-2 immunoblot and negative or indeterminate HIV-1 immunoblot test.

Results

  • Between 1988 and June 2010, a total of 242 suspected cases of HIV-2 were reported to the CDC.
  • 166 of these met the new working definition of HIV-2
  • 47 reported cases were excluded due to insufficient identifying information and 29 did not meet the working definition criteria.
  • These 166 HIV-2 cases represent just 0.01% of the more than 1.4 million U.S. HIV infections diagnosed during 1987-2009.
  • HIV-2 cases were concentrated in the Northeast (66%), including 46% in New York City.
  • Most HIV-2 infections (81%) occurred among people born in West Africa.
  • 89% of people with HIV-2 were black, 58% were men, and the median age at diagnosis was 39 years.
  • Infection risk factors were heterosexual contact (23%), male-to-male sex (2%), injection drug use (2%), and unidentified (72%).
  • The number of HIV-2 cases increased significantly between 1987 and 2009, but this could have been due to changes in surveillance; there were no significant trends during 1990-1999 or 2000-2009.
  • Almost all people with HIV-2 also tested positive for HIV-1 on Western blot antibody tests typically used to confirm positive HIV screening tests (e.g., ELISA).

"Immunoblot antibody tests currently used to confirm HIV reactive screening tests do not contain reagents specific to HIV-2 and thus are not reliable for identification of HIV-2 infections," the report authors wrote. More specialized tests such as the Bio-Rad Multispot HIV-1/HIV-2 rapid test can distinguish between them, however.

"Additional specific testing for HIV-2 should be considered if test results for HIV-1 are inconsistent with one another, inconclusive, or imply the absence of HIV infection despite clinical evidence suggesting its presence, particularly if the patient was born in or had other associations with areas such as West Africa, where HIV-2 infection is prevalent," they recommended. "Suspected HIV-2 cases should be reported to state or local health departments, which can conduct supplemental diagnostic tests for HIV-2 or arrange for them to be done at the CDC laboratory."

Investigator affiliations: Bureau of HIV/AIDS Prevention and Control, New York City Dept of Health and Mental Hygiene, New York, NY; Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA.

8/9/11

Reference

LV Torian, RM Selik, B Branson, et al. HIV-2 Infection Surveillance -- United States, 1987-2009. Morbidity and Mortality Weekly Report 60(29);985-988 (free full text). July 29, 2011.