Jenny’s specific cause of death is never clearly named in the Forrest Gump movie, but it is strongly implied to be a serious, incurable virus such as HIV/AIDS, and later comments from the screenwriter point toward late‑stage HIV as the intended illness.

In the movie itself

  • Jenny tells Forrest she is sick with “some kind of virus” and that the doctors “don’t know what it is,” which fits how new and poorly understood HIV/AIDS was in the early 1980s.
  • The film’s timeline places her illness and death right in the era when the AIDS crisis was emerging in the United States, adding to that implication.

What creators and fans say

  • Screenwriter Eric Roth has discussed that, for a planned but canceled sequel, Jenny’s illness was conceived as late‑stage HIV, reinforcing the idea that HIV/AIDS is what she dies from, even though the original film keeps it vague.
  • Some book and forum discussions mention Hepatitis C as an alternative explanation, partly because of Jenny’s history with injection drug use, but this is never confirmed in the movie and mainly reflects fan interpretation.

Why it’s left ambiguous

  • The film deliberately avoids naming the disease so the focus stays on the emotional impact of Jenny’s death and her relationship with Forrest rather than on medical details.
  • That ambiguity also lets her story echo the broader tragedies of the era—risky lifestyles, the drug culture, and the early AIDS crisis—without turning the film into an issue‑driven drama.

Information gathered from public forums or data available on the internet and portrayed here.