Final answer:
The HTLV-1 virus is associated with IV drug users, healthcare workers, blood transfusion recipients, and sexually active individuals.
Step-by-step explanation:
The HTLV-1 virus, which causes Adult T-cell Leukemia (ATLL), is associated with various groups of people, including IV drug users, healthcare workers, blood transfusion recipients, and sexually active individuals. Therefore, the correct answer is 4) All of the above.