ABC News' Alyssa Newcomb and Anthony Castellano report:

Unsafe sex can be costly, nearly a million dollars in this case.

After four days of testimony and two hours of deliberation, a jury has awarded an Oregon woman $900,000 in damages because she contracted genital herpes after a liaison with a retired dentist.

"The jury essentially said if a person knows he has an STD, he has a duty to inform a sex partner before, not after," said Randall Vogt, the woman's attorney.

Vogt's client, who sued under a pseudonym, met the retired dentist, 69, on an Internet dating website in 2010 and went on three dates, he said. On the fourth, they had sex.

The woman, 49, handed her partner a condom, but his sexual advances took over too quickly, she says.

After intercourse, as the two lay in bed discussing their connection, the man decided to open up and revealed he had herpes, according to the lawsuit. The woman kicked him out of her home.

Eleven days later, the woman had a painful outbreak, which she continues to have periodically. Antiviral medication caused her to lose her hair and she has since gained weight from the drugs she takes to treat the depression caused by the herpes, the lawsuit alleged.

Defense attorney Shawn Lillegren argued that the woman was careless and money-hungry.  "Grow up. Come on. You're an adult. He's an adult. They had sex," Lillegren said, according to the Oregonian.

But the jury didn't buy it, and Tuesday found the man 75 percent liable for negligence and completely liable for civil battery.

Vogt said this kind of lawsuit is "extremely rare" because it's often hard to prove where the victim contracted the STD. He also said embarrassment plays a factor in deterring victims from confronting former partners in court.

He hopes his client set a new precedent.

"When people learn they can be sued for transmitting an STD to another person," he said, "it is going to encourage people to be more careful and less reckless about their contact."