However, this change is so gradual that it is unlikely to have an impact on vaccine design, researchers said.
"Much research has focused on how HIV adapts to antiviral drugs - we wanted to investigate how HIV adapts to us, its human hosts, over time," said lead author Zabrina Brumme, an assistant professor in the Faculty of Health Sciences at Simon Fraser University.
"HIV adapts to the immune response in reproducible ways. In theory, this could be bad news for host immunity - and vaccines - if such mutations were to spread in the population," said Brumme.
"Just like transmitted drug resistance can compromise treatment success, transmitted immune escape mutations could erode our ability to naturally fight HIV," said Brumme.
Researchers characterised the human immunodeficiency virus (HIV) sequences from patients dating from 1979, the beginning of the North American HIV epidemic, to the modern day.
The team reconstructed the epidemic's ancestral HIV sequence and from there, assessed the spread of immune escape mutations in the population.
"Overall, our results show that the virus is adapting very slowly in North America. In parts of the world harder hit by HIV though, rates of adaptation could be higher," said Brumme.
"We already have the tools to curb HIV in the form of treatment - and we continue to advance towards a vaccine and a cure. Together, we can stop HIV/AIDS before the virus subverts host immunity through population-level adaptation," Brumme added.
The study was published in the journal PLOS Genetics.