The HIV pandemic is a complex multi-institutional problem that affects millions of people world-wide. It's an extremely complex system with real-world consequences, and therefore it is fascinating. If you don't think the story belongs on HN, vote other stories up.
From the guidelines:
"On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity."
