SUMMARY: Researchers report in the May 2 edition of the medical journal AIDS (news - web sites) that a California man has been infected with two different strains of HIV (news - web sites).

Researchers report in the May 2 edition of the medical journal AIDS that a California man has been infected with two different strains of HIV, picking up a wild-type (otherwise known as drug-sensitive) strain of HIV after first contracting a drug-resistant strain of the virus.

Initially enrolled in a study that was looking at people with drug-resistant HIV, the man was discovered -- four months after enrolling in the program -- to be infected with more than one strain of HIV. The infection was confirmed after the researchers performed a series of genetic tests to show that the second strain wasn't resistant to reverse transcriptase inhibitors.

The man was infected with HIV strains common in North America. His superinfection apparently had an adverse effect on his health, driving up his viral load in two months from 2,400 to over 200,000, while over the course of 11 months his T-cell count went from a high of over 800 to a low of 282.

HIV superinfection, or the presence of two strains of HIV in the same person, has been a controversial issue in AIDS health and social service circles. It raises issues about HIV-positive people having unprotected sex even with each other, and raises significant stumbling blocks to researchers trying to develop an AIDS vaccine. Activists and health officials also raise concerns about overtalking superinfection, since it could encourage more HIV-infected people to seek out negative partners, which could increase overall infection rates.

Scientists believe current HIV tests used to show if a patient is infected with drug-resistant HIV wouldn't work if the patient also is infected with the wild-type strain. But if the person began drug therapy, evidence of the drug-resistant strain would emerge.

At least two other HIV superinfections have been reported. In September 2002 a Swiss research team reported they had discovered a 38-year-old man with dual strain infections, while in July 2002 at the international AIDS conference in Barcelona, Spain, a researcher reported a similar infected patient in Boston.