Why Do New Strains of HIV Spread Slowly? (IMAGE) PLOS Caption Single strains of HIV entered distinct populations across the world to establish local epidemics. Once established, these epidemics are resilient to the introduction of new strains, thus conserving "founder effects." Credit Ferdinandy et al. Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.