Bill Gates said he twice had to explain to Donald Trump the difference between the HIV and HPV viruses — and that the president’s detailed recollection of Gates’ young daughter’s appearance creeped out his wife, Melinda.

Gates’ remarks came in response to questions from staffers at a meeting of the tech billionaire’s philanthropic Bill & Melinda Gates Foundation, according to MSNBC, which broadcast video of his remarks.

Gates said he had two meetings in Trump Tower where he encouraged the president to take the lead on an effort to speed up progress toward finding a vaccine for HIV.

“Both times he wanted to know the difference between HIV and HPV, and so I was able to explain that those are things that are rarely confused with each other,” Gates said he told Trump.

Human papillomavirus, or HPV, is the most common sexually transmitted infection and can cause health problems including genital warts and cervical cancer.

HIV, or human immunodeficiency virus, weakens the immune system that fights disease and can lead to AIDS. There are vaccines for HPV but no known cure for HIV.

The audience laughed and groaned at Gates’ retelling.

“In both of those two meetings, he asked me if vaccines weren’t a bad thing because he was considering a commission to look into ill effects of vaccines,” Gates said.

“And somebody, Robert Kennedy Jr., was advising him that vaccines were causing bad things and I said, ‘No, that is a dead end, that would be a bad thing, do not do that,’” he said, referring to Kennedy’s fervent belief in the widely debunked theory that vaccines cause autism.

The Microsoft founder also told a story of Trump’s bizarre encounter with Gates’ daughter at a horse show in Florida, where the two chatted for a while before Trump suddenly left.

“And then about 20 minutes later, he flew in on a helicopter to the same place. So clearly he had been driven away but he wanted to make a grand entrance in a helicopter,” Gates said of the show, which took place before Trump’s candidacy for president.

Gates said he met Trump for the first time in New York in December 2016 — and the mogul recalled meeting Gates’ daughter.

“So when I first talked to him, it was actually kind of scary how much he knew about my daughter’s appearance. Melinda didn’t like that too well,” he said.

He also said the meeting got off to a strange start.

“When I walked in, his first sentence kind of threw me off. He said: ‘Trump hears that you don’t like what Trump is doing.’ And I thought, ‘Wow, but you’re Trump.’ I didn’t know the third-party form was always expected. ‘Gates says that Gates knows that you’re not doing things right,’” Gates said.

The White House did not immediately respond to a request for comment.