New research presented December 16 at the American Society for Cell Biology 48th annual meeting in San Francisco suggests that women are more predisposed to contracting HIV via sexual intercourse no matter their vaginal tract presents injuries or not.

Experts have long believed that unless a woman’s vaginal tract is injured, it presents an impenetrable barrier to HIV. But the new study comes to contradict the theory saying that the virus is able to invade the vaginal wall during sexual intercourse and infect immune system cells.

“This is an unexpected and important result. We have a new understanding of how HIV can invade the female vaginal tract. Our perspective is the viruses can infect people in more than one way,” says Thomas Hope, principle investigator and professor of cell and molecular biology at Northwestern University’s Feinberg School of Medicine.

According to data released by the US Centers for Disease Control and Prevention, women account for 26 percent of all new HIV cases in the United States.

For the study, Hope and his colleagues developed a new method for seeing the virus at work. They analyzed newly removed vaginal tissue taken from hysterectomy surgeries and introduced the virus which carried fluorescent, light-activated tracers. Then they saw how the virus penetrated the outer lining of the female genital tract, called the squamous epithelium. HIV was able to reach immune cells, which it targets. The same thing was also observed in nonhuman primates.

The study highlights once again the importance of finding new prevention strategies or therapeutics to block the entry of HIV through a woman’s genital skin, Hope said. For now, the condom appears to be the safest method to prevent infection with the virus, but many men avoid wearing it because they don’t feel comfortable during the intercourse. Other men rejected condoms for cultural and other reasons. But with the new study, the condom seems to be the only way to stay away from a life-long disease.

The researchers also hope that the findings could help in the development of new microbicides and vaccines to protect women against HIV.

According to current estimates by UNAIDS and WHO, by the end of 2007, there were 2.7 million new infections. More than 1 million people are infected with HIV in the United States.

More than one-fifth of Americans living with HIV are unaware of their infection. They are not receiving appropriate care for their condition and can transmit the virus to others. A report released by the CDC found that in 2006, just 40.4% of adults in the U.S. between the ages of 18 to 64-years old were tested for HIV. From 2001 through 2006, the testing rate stalled. According to current estimates, 34 percent of new infections occur in persons aged 30 to 39.