There are multiple strains of hiv. One of the papers I linked to is a detailed study investigating a less lethal, more infectious strain. Sars-cov1 also evolved

There are multiple strains of hiv. One of the papers I linked to is a detailed study investigating a less lethal, more infectious strain. Sars-cov1 also evolved a few strains that were more infectious and less lethal. Both effects, by the way, are usually associated with separate individual mutations. It's rare that a single change in DNA results in both effects.