Worldwide, nearly 40 million people are infected with HIV, the virus that causes AIDS. Here's the Quick Fire Science, with Phil Sansom... HIV is the human immunodeficiency virus, and around one in 650 people have it in the UK. Often the only symptom is a short flu-like illness a few weeks after infection, which lasts for a week or two. However, long after this symptom disappears, HIV is infecting and damaging vital cells in your immune system. This can lead to AIDS, or acquired immunodeficiency syndrome.If you have AIDS, your immune system has been severely damaged by HIV. You become... Like this podcast? Please help us by supporting the Naked Scientists