HIV-2 is neither as widespread nor as virulent as HIV-1, a strain of HIV that accounts for the majority of infections in the ongoing epidemic. Perhaps it is because of this that less research has focused on HIV-2 compared to on HIV-1. However, in a recent study, a team of European and American researchers examined the correlation between male circumcision—which has been linked to reduced HIV-1 prevalence in the past–and rates of HIV-2.
Largely found in West Africa, HIV-2 infection can progress to AIDS but is marked by slower disease progression, lower infectiousness in early stages, and lower mortality than HIV-1. Cases of this less common form of the virus have also been found in France, Spain, Portugal, and former Portuguese colonies, which have ties to West Africa. Due to genetic differences between the two virus strains, most HIV tests screen exclusively for the antigens for the more prevalent strain of the virus, HIV-1, but now, tests are available to detect the antibodies for both strains.
According to the World Health Organization (WHO), there is meaningful evidence that male circumcision (MC)—surgical removal of the foreskin–reduces the rate of heterosexually-acquired HIV by about 60%, as the foreskin is more susceptible to HIV infection. Though it only provides partial protection and must be offered in conjunction with prevention initiatives, including safe sex education and testing services, circumcision is considered an effective intervention in areas with high rates of HIV and heterosexual epidemics, and low rates of circumcision. Health officials in HIV-stricken areas recommend circumcision as a low-cost way to prevent males from acquiring HIV and other sexually transmitted diseases.
Although there has been a series of studies supporting MC as a method of preventing HIV-1 transmission, a team led by University of Leuven researchers in Belgium recently conducted the first investigation into the association between circumcision and HIV-2 prevalence. The study was recently published in PLOS One, and in it, the authors noted that the practice of circumcision in West Africa was not common until after the early 20th century; nevertheless, today, it is almost universal in the region. The authors hypothesized that different rates of circumcision in parts of the region would correlate with variations in HIV-2 rates. However, due to lack of data focusing on HIV-2 prevalence, they had to combine serological data from West African cities with information from databases on historical patterns of circumcision in order to calculate the correlation between HIV-2 and circumcision rates.
The researchers analyzed more than 260,000 samples collected in 16 West African countries during the first large-scale serological study of HIV-2 from 1985 to 1991, soon after the discovery of the virus. They compared those findings to information on MC rates in 218 ethnic groups in the region. The authors noted that rates of circumcision likely rose during the 20th century due to the spread of Islam—which holds circumcision as a common practice—into areas where circumcision had not been common. In their investigation, the researchers found a robust correlation between HIV-2 seroprevalence and historical prevalence of male circumcision.
“We calculated MC frequencies for ethnic groups and cities over time, and we found, as far as we know for the first time, that HIV-2 prevalence in 1985—91, in West Africa, shows a substantial ecological association with MC, as has been demonstrated for HIV-1, for Africa as a whole, at about the same time period,” wrote the authors in their paper.
From their findings, the authors also examined how circumcision rates in the early 20th century—when HIV-2 is believed to have first emerged—may have influenced where the disease initially took hold. “Differential HIV-2 spread could also reflect viral founder events. Cities with higher HIV-2 prevalence in 1985—91 might have imported the virus earlier, therefore the epidemic focus might have had more time to grow,” explained the authors, noting that circumcision frequency was markedly lower in the cities of Côte d'Ivoire and Guinea-Bissau, the only demonstrably old epicenters of HIV-2. “Indeed, founder events may have been more probable (and might therefore have tended to happen earlier) in cities with increased transmission risk factors, including low MC frequency.”
The authors concluded that their findings reinforce the public health benefits of circumcision in preventing the spread of not just HIV-1, but also HIV-2 and other retroviruses.