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African Study Finds HIV Superinfection May be as Common as Initial Infection

HIV superinfection may occur much more often than previously believed, and in fact may occur about as often as first-time infections, according to a study from Uganda described in the June 15, 2012, advance online edition of the Journal of Infectious Diseases.alt

Superinfection refers to infection with a second or subsequent strain of HIV in a person who is already infected with another. Several prior studies -- mostly in high-risk populations such as sex workers -- have suggested that superinfection is uncommon, and most likely to occur during the first years after initial infection. Superinfection may accelerate disease progression, but outcomes are not well understood.

Researchers with the U.S. National Institute of Allergy and Infectious Diseases (NIAID), Johns Hopkins, and Makerere University conducted a large-scale study of HIV superinfection in a general heterosexual population in Africa -- the first of its kind, according to the researchers.

Using a novel, high-throughput "ultra-deep sequencing" technique, the researchers determined the superinfection rate by examining 2 regions of the HIV genome (p24 and gp41) in blood samples from 149 recent seroconverters in Rakai, Uganda.


  • 7 cases of superinfection were identified among the 149 participants, a rate of 1.44 per 100 person-years.
  • This compares with a first-time HIV infection rate of 1.15 per 100 person-years among the Rakai general population -- not significantly different from the superinfection rate.
  • After controlling for baseline sociodemographic and behavioral factors, the primary incidence rate in the general population was higher, at 3.28 per 100 person-years.
  • Superinfections included both same-subtype (D-D, 4 cases) and different-subtype (D-A, 3 cases) infections.

These findings, the study authors concluded, "[suggest] that the rate of HIV superinfection in a general population is substantial, which could have a significant impact on future public health and HIV vaccine strategies."

Almost all cases of HIV transmission in this cohort occurred via vaginal intercourse, and therefore the findings may not be generalizable to groups with other modes of transmission such as men who have sex with men, they noted.

"There is previous evidence that HIV superinfection can have detrimental clinical effects, even in individuals who were previously controlling their HIV infection," they elaborated in their discussion. "These data suggest that post-test counseling of HIV-infected individuals needs to emphasize the risk of HIV superinfection and the possible clinical implications of continued unsafe behaviors."

Our findings suggest that HIV vaccine strategies designed to recreate the natural immune response to HIV may be insufficient to protect an individual from infection," Redd said in a press release issued by NIAID. "However, the data also provide an interesting new population to explore since it is possible that some individuals will be protected from superinfection. Determining what controls superinfection could lead to new avenues for vaccine research."



AD Redd, CE Mullis, D Serwadda, et al. The Rates of HIV Superinfection and Primary HIV Incidence in a General Population in Rakai, Uganda. Journal of Infectious Diseases. June 5, 2012 (Epub ahead of print).

Other Sources

National Institute of Allergy and Infectious Diseases. HIV superinfection in Uganda may be more common than previously thought, study finds. NIH News. June 7, 2012.

Johns Hopkins Bloomberg School of Public Health. New Data Suggests HIV Superinfection Rate Comparable to Initial HIV Infection. Press release. June 7, 2012.