HIV-2 Infection Surveillance -- United States, 1987-2009

By Lucia V. Torian, Ph.D., Richard M. Selik, M.D., Bernard Branson, M.D., S. Michele Owen, Ph.D., Timothy Granade, M.S., R. Luke Shouse, M.D., M. Patricia Joyce, M.D., Danuta Pieniazek, Ph.D., Richard Kline, M.S.
From U.S. Centers for Disease Control and Prevention

July 29, 2011

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Editorial Note

The results of the analyses described in this report indicate that HIV-2 infections in the United States are rare, concentrated in the Northeast, and limited mainly to persons born in West Africa. Regional differences in the percentage of reported HIV cases caused by HIV-2 might be, in part, a result of the nonuniform geographic distribution of U.S. residents born in West Africa. New York is a major gateway for African immigrants to the United States.⁸

However, regional differences in the percentage of HIV cases caused by HIV-2 also could be the result of variations in completeness of diagnosis and reporting of HIV-2 by laboratories and state HIV surveillance programs. In particular, the large percentage of HIV-2 cases reported from New York City might have resulted, in part, from an increased focus on ascertainment of HIV-2 cases by the New York City Department of Health and Mental Hygiene, which has conducted active investigations to identify HIV-2 infections⁹ and issued an advisory to clinicians regarding diagnostic testing for HIV-2. The percentage of HIV-2 diagnoses based on an HIV-2 DNA test was several times higher among cases reported from New York City (68%), where many cases were diagnosed by the city's public health laboratory, than among cases from the four other regions (range: zero to 26%).

The findings in this report are subject to at least three limitations. First, the surveillance case definition for HIV infection and the working HIV-2 definition used in this analysis are intended primarily for analysis of epidemiologic trends and associations and might be inappropriate for other purposes, such as the clinical management of patients, which might require diagnostic considerations beyond the criteria used for the case definition. CDC currently is reviewing the HIV surveillance case definition to identify areas for revision, including the addition of specific criteria for HIV-2. Second, the 166 HIV-2 infections described in this report are likely an underestimate of HIV-2 cases in the United States. Many of the 76 suspected cases excluded from the analysis because of inadequate data on test results or missing identifiers might be actual HIV-2 cases. Other cases might not have been diagnosed because diagnostic tests specific for HIV-2 (e.g., DNA test or type-differentiating antibody immunoassay) were not widely used, and some cases might not have been recognized because of negative or persistently indeterminate results on assays designed primarily to detect HIV-1 antibodies. Finally, although 11% of HIV-2 cases had nucleic acid evidence of possible coinfection with HIV-1, the full extent of coinfection could not be assessed because HIV-1 nucleic acid test results were missing for 49% of the HIV-2 cases. In addition, 13 of the 17 detectable HIV-1 viral loads were <5,000 copies/mL, raising the possibility that they might be falsely positive.

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. 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. In every state, confirmed HIV infection diagnoses are required by law or regulation to be reported to the health department.

References

O'Brien TR, George JR, Holmberg SD. Human immunodeficiency virus type 2 infection in the United States. JAMA 1992;267:2775-9.
CDC. Testing for antibodies to human immunodeficiency virus type 2 in the United States. MMWR 1992;41(No. RR-12).
De Cock KM, Brun-Vézinet F, Soro B. HIV-1 and HIV-2 infections and AIDS in West Africa. AIDS 1991;5(Suppl 1):S21-8.
Ntemgwa ML, d'Aquin Toni T, Brenner BG, Camacho RJ, Wainberg MA. Antiretroviral drug resistance in human immunodeficiency virus type 2. Antimicrob Agents Chemother 2009;53:3611-9.
Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. Washington, DC: US Department of Health and Human Services; 2011. Accessed July 25, 2011.
CDC. Revised surveillance case definitions for HIV infection among adults, adolescents, and children aged <18 months and for HIV infection and AIDS among children aged 18 months to <13 years -- United States, 2008. MMWR 2008;57(No. RR-10).
De Cock KM, Porter A, Kouadio J, et al. Cross-reactivity on Western blots in HIV-1 and HIV-2 infections. AIDS 1991;5:859-63.
Grieco EM, Trevelyan EN. Place of birth of the foreign-born population: 2009. American Community Survey briefs. Washington, DC: US Census Bureau, 2010. Accessed July 27, 2011.
Torian LV, Eavey JJ, Punsalang AP, et al. HIV type 2 in New York City, 2000-2008. Clin Infect Dis 2010;51:1334-42.

What is already known on this topic?

Of the two types of human immunodeficiency virus (HIV), HIV-1 accounts for most HIV infections worldwide and, untreated, causes acquired immunodeficiency syndrome (AIDS). HIV-2 is rarely reported in the United States, largely confined to persons from West Africa, and less likely to cause AIDS. Distinguishing between HIV-2 and HIV-1 is important because their clinical management differs; HIV-2 does not respond to some antiretroviral drugs effective on HIV-1, and HIV-2 cannot be measured by HIV-1 viral load tests.

What is added by this report?

Using a working case definition for HIV-2 infection, CDC identified 166 cases diagnosed during 1987-2009. Most cases (66%) were reported from the Northeast, particularly New York City (46%). A total of 132 (81%) cases were in persons born in West Africa. Most (60%) HIV-2 cases had positive HIV-1 immunoblot test results, indicating that the usual tests for HIV-1 infection can misclassify HIV-2 cases as HIV-1 unless other tests (e.g., DNA test or type-differentiating antibody immunoassay) specific for HIV-2 are used.

What are the implications for public health practice?

Specific testing for HIV-2 should be considered if results of tests 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 is from West Africa. Suspected HIV-2 cases should be reported to state or local health departments, which can conduct supplemental tests for HIV-2 or arrange for testing at CDC. If the type of HIV is identified as HIV-2 after an HIV case is reported, the report should be updated with the type specified as HIV-2.

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This article was provided by U.S. Centers for Disease Control and Prevention. It is a part of the publication Morbidity and Mortality Weekly Report. Visit the CDC's website to find out more about their activities, publications and services.