The dominant strain of HIV in the U.S. is becoming "more infectious" and "virulent" via the process of "natural selection," researchers have found. This suggests that while HIV might be on the decline thanks to public health measures, the virus that remains appears to be more transmissible today than it was in the past.
Researchers from the University of California San Diego (UCSD), working alongside scientists at the U.S. Centers for Disease Control and Prevention (CDC) were looking at the sub-type B strain of HIV that is found across the U.S. They published their findings in Nature Communications in December.
"The remarkable thing about evolution by natural selection is its inevitability," co-author Joel Wertheim, an assistant professor at the UCSD, told Newsweek. "Viruses, like all organisms, adapt and evolve. And our study suggests that HIV circulating today is slightly more transmissible than the HIV from a decade ago."
This is not a cause for "panic," he added—"tools available to public health officials and doctors mean that we can still effectively treat people infected with HIV and prevent infection in people exposed to HIV."
There are a number of factors that might increase the rate of HIV transmission. Most significantly, the actions of people carrying HIV—for example, do they take antiviral treatment as prescribed? Do they engage in unsafe sex?
Another factor is viral load. This is the concentration of HIV in the bloodstream. The higher the load, the more infectious the virus and the quicker the progression of the disease. This means that someone with a higher load—a trait inherited from the original host—will develop faster than someone with a lower load, if the virus is left untreated.
But while a higher viral load might increase the risk of HIV transmission, it might not increase the rate of HIV transmission. This is because it speeds up the disease progression process, giving the virus less time to spread before the person infected dies.
As the success of the less virulent, less infectious HIV-1 subtype A shows, a slower disease progression can aid the spread of the virus.