HIV-2 is one of two types of human immunodeficiency virus that can cause AIDS. It is far less common than HIV-1, the type responsible for the vast majority of HIV infections worldwide, and it follows a notably slower disease course. Most people with HIV-2 live in West Africa or have ties to that region, and many will go years or even decades before developing symptoms.
How HIV-2 Differs From HIV-1
HIV-1 and HIV-2 both attack immune cells and can eventually lead to AIDS, but they are genetically distinct viruses with separate origins. HIV-1 jumped to humans from chimpanzees, while HIV-2 crossed over from sooty mangabeys, a species of monkey found in West Africa. These were entirely independent events. At the genetic level, the two viruses share only about 55% of their DNA sequence, and some of their surface proteins are as little as 35% identical. That degree of difference has real consequences for how the virus behaves in the body, how it responds to treatment, and how it’s detected in lab tests.
One of the most striking biological differences involves the immune system’s ability to fight back. In HIV-1 infection, the virus’s outer surface is heavily shielded by sugars and structural tricks that prevent antibodies from latching on. HIV-2’s surface is far more exposed. The immune system produces high levels of broadly neutralizing antibodies against HIV-2, something that rarely happens with HIV-1. This stronger antibody response is one reason HIV-2 progresses more slowly and is harder to transmit.
Where HIV-2 Is Found
HIV-2 is concentrated in West Africa. Countries with notable prevalence include Guinea-Bissau, Cabo Verde, Burkina Faso, Côte d’Ivoire, Mali, Gabon, and Cameroon. Among HIV-positive individuals tested across eight countries in that region, roughly 3% carried HIV-2 rather than HIV-1. Guinea-Bissau has historically had the highest rates.
Outside West Africa, cases are uncommon but not absent. In Europe, Portugal and France have the most documented infections, with approximately 2,000 and 1,000 cases respectively, largely linked to migration from former colonies. In the United States, the CDC reported 198 cases between 2010 and 2017. India has also recognized a meaningful number of infections. Overall surveillance remains limited, and experts consider current diagnostic testing inadequate for accurately measuring the true global burden of HIV-2.
Slower Progression and Better Survival
The most important clinical distinction is speed. HIV-2 moves through the body far more slowly than HIV-1. Plasma viral loads (the amount of virus circulating in the blood) tend to be much lower, and the immune system’s key defensive cells decline at a slower rate. Many people with untreated HIV-2 remain in the asymptomatic stage for years longer than those with HIV-1.
A long-term cohort study in Guinea-Bissau put numbers to this: the median survival time from infection was 15.6 years for HIV-2, compared to 8.2 years for HIV-1, both without treatment. Some people with HIV-2 never progress to AIDS at all and maintain stable immune function for decades. That said, HIV-2 can and does cause AIDS. A slower timeline is not the same as no risk.
Transmission Is Less Efficient
HIV-2 spreads through the same routes as HIV-1: sexual contact, blood exposure, and from parent to child during pregnancy or breastfeeding. But it is significantly harder to transmit. Sexual transmission rates are about five times lower than for HIV-1. The difference is even more dramatic for mother-to-child transmission, which occurs at 20 to 30 times lower rates.
A systematic review of perinatal transmission found that among pregnant women with HIV-2 who were not on treatment, the rate of passing the virus to their babies was just 0.2%. Several studies put the range at 0% to 4%, compared to roughly 15% to 45% for untreated HIV-1. Lower viral loads in the blood, stronger immune cell counts, and less viral shedding in the genital tract all contribute to this reduced infectiousness.
How HIV-2 Is Diagnosed
Standard HIV screening in the U.S. now uses a combination test that detects antibodies to both HIV-1 and HIV-2, along with a specific HIV-1 protein. If that initial test comes back reactive, the sample moves to a second test designed to distinguish between HIV-1 and HIV-2 antibodies. If that differentiation test is unclear, a genetic test for HIV-1 viral material helps sort out the diagnosis.
This two-step process matters because treatments differ between the two viruses. Older testing methods could miss HIV-2 entirely or misidentify it as HIV-1, which could lead to prescribing drugs that don’t work against HIV-2. If you have risk factors for HIV-2, specifically travel to or origins in West Africa, or a sexual partner from that region, making sure your provider knows this can help ensure the right tests are ordered.
Treatment Differences
HIV-2 can be treated with antiretroviral therapy, but not all HIV drugs work against it. The virus is naturally resistant to an entire class of medications commonly used for HIV-1 (non-nucleoside reverse transcriptase inhibitors, a mainstay of many standard regimens). This means treatment plans need to be specifically tailored. Some other drugs that work well for HIV-1 have reduced or uncertain effectiveness against HIV-2.
Monitoring also looks different. With HIV-1, tracking viral load is the primary way to know if treatment is working. For HIV-2, that’s not sufficient on its own. Disease progression can occur even when viral load tests show the virus is undetectable. People with HIV-2 need ongoing immune cell count monitoring regardless of what their viral load reads. This quirk makes management trickier and requires clinicians experienced with HIV-2, which can be a challenge in regions where the virus is rare.
Living With HIV-2
For most people diagnosed with HIV-2, the outlook is considerably better than for HIV-1. The slower progression, lower viral loads, and reduced transmissibility all work in the patient’s favor. Many individuals live with HIV-2 for years before needing treatment, though current guidelines generally recommend starting therapy regardless of symptoms to prevent long-term immune damage.
The main challenges are practical. HIV-2 is rare enough outside West Africa that many healthcare providers have limited experience with it. Diagnostic tools and viral load assays are less standardized than for HIV-1. Research funding and drug development have overwhelmingly focused on HIV-1, leaving fewer clinical trials and less data to guide HIV-2 treatment decisions. For people living with HIV-2 in non-endemic countries, connecting with an infectious disease specialist familiar with the virus is often the most important first step.