How do i make some sub-categories not to all adding questions?

Question

Hello,

I would like to have many sub-categories under "Health". But still under health, i would like also to have there some sub-categories of  as below;

Health (main category)
1. Diseases/Conditions         (This sub-category under health should not allow members to add questions except the categories under it as below)
-HIV/AIDS
-Allergies

-Alzheimer's Disease

-Arthritis

-Asthma

-Cancer

 

So how do i achieve that above?

 

Your help will be highly appreciated

 

Thank you

Ronnie