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HIV transmission through heterosexual sex: new findings
Last reviewed: 01.07.2025
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A new study shows that while HIV infection varies from person to person over time, the strains of the virus that are transmitted through heterosexual sex are often identical to those that the carrier partner was previously infected with. Understanding the characteristics of these strains could help in the fight against HIV. The scientists who conducted the study and made the discovery hope that their findings will be a step toward creating an HIV vaccine.
The study was led by researchers Andrew Redd and Thomas Quinn of the National Institute of Allergy and Infectious Diseases.
A team of scientists studied the genetic patterns of HIV infection using blood samples from heterosexual patients in Uganda, which were collected between 1994 and 2002.
The experts were able to detect a significant increase in genetically modified HIV viruses among infected people over the entire eight-year period. Interestingly, these changes occurred in some people, not in all infected people.
To explain this phenomenon, scientists proposed that the genetic diversity of HIV at the population level was limited because only certain strains of the virus were responsible for subsequent sexual transmission.
To test their theory, the researchers studied the genetic relationship of strains of the infection in 31 couples where transmission occurred through heterosexual contact.
In 22 cases, the virus in the blood of the infected partner was the same form as that of the partner who transmitted the virus in the early stages after infection.
According to Dr. Redd, this discovery suggests that heterosexual transmission of HIV infection naturally selects for virus strains early in transmission, reducing viral diversity at the population level.
Research by other scientists confirms that the virus detected in the early stages differs little from the strain that caused the infection.
Thus, the infected person's body somehow retains a minimal amount of the virus strain, which can subsequently infect another person during sexual contact. It follows that this strain has an evolutionary advantage over other HIV strains, since it can overcome the sexual barrier without changes and provoke an infection, emphasizes Dr. Redd.