Human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) both cause AIDS. Following the licensure of combination HIV-l/HIV-2 screening enzyme immunoassays, the FDA recommended that beginning in June 1992, all donated whole blood, blood components, and source plasma be screened for antibody to HIV-2, because not all persons infected with HIV-2 can be detected by HIV-1 testing [1,2]. This report describes the first two cases of HIV-2 infection detected among potential blood donors since the implementation of recommended HIV-2 screening, and summarizes national data about persons known to be infected with HIV-2 during December 1987 to June 1995.
Donor 1
In June 1994, a blood donation was discarded after it tested positive by combination HIV-1/HIV-2 enzyme immunoassay and indeterminate by HIV-1 Western blot assay. The donor was notified about the test results and consented to an interview and repeat testing. Testing at the CDC indicated that the specimen was positive by HIV-1 enzyme immunoassay, HIV-1 Western blot assay, HIV-2 enzyme immunoassay, and HIV-2 Western blot assay research use only. Results of research use only synthetic peptide tests indicated cross-reactivity to HIV-1 and were interpreted as HIV-2 infection.
The donor was born and resided in the United States. She had not previously donated blood or plasma. She reported no symptoms related to HIV infection, and denied use of intraveous drugs, receipt of transfusions, and travel outside the United States. Since 1982, she had had four male sex partners, all born in the United States. The HIV status of her partners is unknown, and she was unaware of any HIV infection risks among them. She has no children. She received HIV counseling-including instructions to refrain from donating blood, blood components, and tissues or organs-and was referred to a health-care provider.
Donor 2
In November 1994, a plasma donation was destroyed after the serum tested positive by combination HIV-1/HIV-2 enzyme immunoassay and research use only HIV-2 Western blot assay. Attempts by the plasma center to notify the donor were unsuccessful. However, the donor independently sought HIV testing 2 weeks later at a counseling and testing site. In these tests, the HIV-1 enzyme immunoassay was positive and HIV-1 Western blot assay was atypical with an indeterminate band pattern suggestive of HIV-2 infection. Subsequent testing at the CDC indicated the specimen was HIV-1 enzyme immunoassay positive, HIV-1 Western blot assay indeterminate, HIV-2 enzyme immunoassay positive, and HIV-2 Western blot assay positive. Research use only synthetic peptide enzyme immunoassay and dot blots were also positive for HIV-2. These results were interpreted as confirming HIV-2 infection.
During the follow-up interview, the male donor reported no symptoms of HIV infection. He had not previously donated blood or plasma. He was born in France and had lived in several countries in western Africa during 1979-1985, before moving to the United States. While in western Africa, he was vaccinated on two occasions with needles that were wiped with cotton and reused between patients. He also received several tattoos in Africa. Of his estimated 35 lifetime sex partners, most were African. The donor denied having had sex with men, using intravenous drugs, and receiving transfusions. He received HIV counseling-including instructions to refrain from donating blood, blood components, and tissues or organs-and was referred to a health-care provider.
US Reports of HIV-2 Infection
As of June 30, 1995, a total of 62 persons with HIV-2 infection were reported in the United States (Figure 1). Of 58 persons for whom gender data were available, 38 (66%) were male. At least 11 of the 62 persons had an AIDS-defining condition at the time of report, and 5 are known to have died. Of these 62 persons, 42 (68%) were born in western Africa and 2 in Europe; for 9, the region of origin was unknown, although 4 had malaria antibody profiles consistent with previous residence in western Africa. Of the nine persons with HIV-2 infection born in the United States, six were adults, of whom four had either traveled to or had a sex partner from western Africa, and three were infants born to mothers of unknown national origin.
Editorial Note from the CDC
In the United States, HIV-2 infection among blood donors is extremely rare. Since the implementation of combination HIV-1/HIV-2 enzyme immunoassay screening of blood and plasma donations, an estimated 74 million donations have been tested for HIV. Including the two cases described in this report, three cases of HIV-2 infection have been detected among blood and plasma donors in the United States; the first case was detected by HIV-1 screening in 1986 [3]. These findings are consistent with previous surveys of approximately 20 million US blood donations during 1987-1989, in which no blood-donor specimens with HIV-2 antibody were detected [4,5].
The national blood supply is protected from HIV primarily through two methods:
- Interviewing donors about risk behaviors for HIV infection
- Laboratory screening donations for HIV [6,7].
All donations detected with HIV are excluded from any clinical use (21 CFR 610.45(c)) , and donors are deferred from further donations (21 CFR 606.160(e)). For both donors described in this report, although no HIV risk factors were identified during the interview preceding blood donation, laboratory screening of their blood and plasma donations detected HIV infection. Subsequent testing revealed HIV-2 cross-reactivity, resulting in a positive HIV-1 enzyme immunoassay (which would have led to exclusion even in the absence of HIV-2 testing) and a positive or indeterminate HIV-1 Western blot assay.
Human immunodeficiency virus type 1 is distributed worldwide and is prevalent in the United States; however, HIV-2 is endemic in western Africa, with limited distribution to other regions of the world. Of the 62 persons reported with HIV-2 infection in the United States, at least 48 (77%) were born in, had traveled to, and/or had a sex partner from western Africa.
In addition to detection of HIV-2 cases through blood and plasma donor screening, epidemiologic data about HIV-2 cases are collected through the CDC-supported national HIV/AIDS surveillance system and serosurveys [8,9]. Because not all persons who are infected with HIV-2 donate blood or are otherwise tested for HIV-2, the number of persons reported with HIV-2 infection probably is underestimated. Nonetheless, the data from these sources indicate that HIV-2 is uncommon in the United States.
Blood centers detecting a repeatedly reactive specimen by combination HIV-l/HIV-2 enzyme immunoassay should follow the recommended CDC/FDA testing algorithm [1]. Specimens suspected of being HIV-2 positive may be referred to state health department laboratories or to the CDC for confirmatory HIV-2 testing. Cases of HIV-2 infection should be reported to state and local health departments, as allowed by law and/or regulation. Periodic updates about the number of persons known to be infected with HIV-2 in the United States are available from the CDC National AIDS Clearinghouse.
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