Bill Gates told an audience recently that President Donald Trump did not seem to know the difference between HIV and HPV. Gates made the remarks shortly after meeting with the president. “He wanted to know if there was a difference between HIV and HPV. So I was able to explain that those are rarely confused with each other,” Gates said in a video clip obtained by MSNBC’s All In. HIV is the human immunodeficiency virus that affects the immune system and can lead to AIDS, while HPV is the human papillomavirus, a common sexually transmitted infection that is mostly harmless.