In the last decade, millions more people in the developing world have gained access to anti-viral drugs to treat HIV, with nearly 12 million now on this life-giving treatment. But with more people on medication, there’s concern about the spread of drug-resistant strains of the virus, which can be transmitted from one individual to the next.
A new, multi-center study led by Stanford researchers offers some good news on this front: The transmission of drug-resistant strains thus far has been fairly limited in the hard-hit regions of Africa and Asia. The research involved more than 50,000 patients in 111 countries.
It is inevitable that transmitted drug resistance will increase further, so we need to continue ongoing monitoring to ensure successful, long-term treatment outcomes
“What we are showing is that the rates of transmitted drug-resistant HIV in the low- and middle-income countries most affected by HIV have increased modestly,” Stanford infectious disease expert Robert Shafer, MD, principal investigator on the study, told me. “The rate of increase in sub-Saharan Africa has been low, and an increase has not been detected in south Asia and Southeast Asia.”
Shafer is nonetheless cautious, as drug resistance remains a problem in these regions, where patients are prescribed drug regimens that are not as effective as those used in the West. And adhering to a daily regimen can be challenging for these patients, as transportation, drug supply and other issues may get in the way. Resistance can occur when there is a gap in treatment.
“It is inevitable that transmitted drug resistance will increase further, so we need to continue ongoing monitoring to ensure successful, long-term treatment outcomes for the millions of people on therapy worldwide,” Shafer said.
In the study, he and his colleagues identified four mutations that were linked to resistance to two HIV drugs, nevirapine and efavirenz. That result points to the possibility of creating a simple test that could be used to detect these mutations, he said. Clinicians then could tailor their treatment accordingly.
Another key finding was that the drug-resistant strains that did occur were not from a single line of resistant viruses, but were quite distinct. That means they developed independently, not as a result of a single transmission chain. That differs from some other microbes, such as malaria and tuberculosis, where resistant strains can move very quickly through the population.
“We are finding that the strains being detected in low-income countries are pretty much unrelated to one another,” Shafer said. “So that suggests these have not yet gained a foothold in the population and are less often being transmitted among people who have never received the drugs before.”
The study appears online today in PLoS Medicine.