Final answer:
It is false that HIV was introduced into humans only once from SIV; it likely occurred multiple times during zoonotic transfers. HIV originated in sub-Saharan Africa and is now a global pandemic, not limited by sexual orientation in its transmission.
Step-by-step explanation:
The statement that HIV was introduced into humans only once, from simian immunodeficiency virus (SIV), is false. HIV is believed to have originated in sub-Saharan Africa during the 20th century, transmitted from primates to humans on more than one occasion through a process known as zoonosis.
The transmission occurred probably sometime during the early to mid-1900s, most likely in West Africa, before the virus spread globally. Subsequent mutations and different strains of the virus emerged as HIV adapted to its human host.
It is crucial to understand that HIV is a blood-borne, sexually transmitted disease that does not discriminate based on sexual orientation, as it can be transmitted through heterosexual and homosexual contact alike.