WATCH: Danny Pintauro on How He Contracted HIV

After having revealed to Oprah Winfrey that he's been HIV-positive for 12 years, former child star Danny Pintauro has disclosed how he believes he contracted the virus -- through oral sex.

The onetime Who's the Boss? cast member says he was religious about safer-sex practices because he was so paranoid about HIV, but he let his guard down because of his drug use -- he was at one point addicted to crystal meth.

"Believe it or not, with this guy [from who he contracted the virus], I was actually safe," he told Us magazine in a video interview posted online Monday. "We did use condoms. I got it another way, which was through oral sex, which is a complicated story. When you put all these things together, like a compromised immune system, having been up for a long time, rough sex, lesions in your mouth, maybe, mixing of bodily fluids, it's that easy."

The Centers for Disease Control and Infection notes that the risk of HIV transmission during oral sex is not as great as during anal or vaginal sex, but oral sex is not risk-free. "Even though oral sex carries a lower risk of HIV transmission than other sexual activities, the risk is not zero," the CDC's website cautions. "It is difficult to measure the exact risk because people who practice oral sex may also practice other forms of sex during the same encounter."

"Performing oral sex on an HIV-infected man, with ejaculation in the mouth, is the riskiest oral sex activity," the site further states. "Factors that may increase the risk of HIV transmission through oral sex are oral ulcers, bleeding gums, genital sores, and the presence of other sexually transmitted diseases." Risk can be reduced by using condoms or other barriers during oral sex or by avoiding ejaculation in the mouth, the CDC adds.

The CDC also notes that while injection-drug use is a direct route of transmission, other types of drug use lower inhibitions, making people more likely to engage in risky behavior.

Pintauro did not provide additional details about the transmission or his sexual partner in the encounter, but said he is trying to find the man. He had forgotten the man's name until he ran across it in an email, he told Us.

Below, watch the interview, in which Pintauro also discusses how he met his husband, Wil Tabares; the challenge of finding an understanding partner when you're HIV-positive; and the support he's received from Who's the Boss? cast mates Judith Light, Tony Danza, and Alyssa Milano.