A Mississippi baby born with the AIDS virus appears to have been cured after being treated with an aggressive regimen of drugs just after her birth 2½ years ago, an unusual case that could trigger changes in care for hundreds of thousands of babies born globally each year with HIV.

The findings, reported Sunday by researchers, mark only the second documented case of a patient being cured of infection with the human immune-deficiency virus. The first, an adult man known as the Berlin patient, was cured as a result of a 2007...