Let's assume the HIV virus really existed. Now this is redundant if the V in HIV stands for virus.
Anyway if people could be infected with the HIV virus even before the HIV virus was discovered then people can have a physical condition that is not yet classified as a type of physical condition.
Now there are many types of cognitive impairments due to known physical conditions but there could also be types of cognitive impairments due to unknown physical conditions.
Most people could be...
@shortstories
Easier explanation: they're cursed.
What kind of curse that does what and how did they get cursed?