Opportunistic infections (OIs) are infections that occur more frequently and are more severe in individuals with weakened immune systems, including people with HIV.
Being nostalgic means to miss the past time. It seems that a real life was in the past because now in the present is different, probably things changed and we know that never is going to be the same. It leads to a nostalgic feeling.
a : afraid or nervous especially about what may happen : feeling anxiety. 1  She feels anxious and depressed. 2  They are anxious [=worried, concerned] about their son's health. 3  People are anxious about the future.  They were anxious for their daughter. [=they were worried about what might happen to their daughter]