Since AIDS is caused by viruses,it can be said as viral disease.But,it can also be categorised based on the way of transmition of the virus(example:also classified as sexually transmitted desease(STD))
AIDS is causes by a virus called HIV (human immunodeficiency virus). Hence it's causative organism is HIV virus.
Causes of AIDS...
1. It is transmitted to another person when an infected person establishes a sexual relationship with other person.
2. It could also transmitted through blood. When a infected person's blood is given to other person
3. It also causes by using the same needle which is used on an infected person.
4. One may inherent it from their parents.