Episodes airing this month have seen Val (Charlie Hardwick) learn that she may have contracted HIV when she had a fling on holiday. However, she has so far refused to get herself tested.
Speaking on ITV's This Morning about the story, Oates commented: "It's one I'm really proud of. It's about HIV in a straight, middle-aged white married woman, which is not a story that I think soap has tackled yet. Obviously for a lot of soap fans, the last time they came across HIV in a big soap was EastEnders' Mark Fowler, which was a fantastic story and very much of its time.
"Things have changed so dramatically and I suppose I just wanted to tell a story that informed people properly, and made people realise that actually their preconceptions of what HIV is today really probably aren't right."
She continued: "What's interesting is that Val shares the stigmas that I sort of want to bust through, really. She's a woman of a certain generation.
"What she doesn't do is go and get tested, because she's frightened. She buries her head in the sand and she's not talking to the man who really loves her, Eric, about how they might get through this."
In next week's episodes, Val confides in Victoria Sugden about the situation, but continues to shy away from telling Eric the truth.
Oates also discussed other upcoming stories for Emmerdale, promising that gay character Finn Barton (Joe Gill) will have a love interest.
"I love Finn Barton. Finn is the square peg in the round hole as far as the Bartons are concerned," she explained. "He's not the burly farming type - he's got his iPad and reads The Economist. There will be [a love interest], but at the moment he's got his BFF in Victoria, so he's sticking with her."
She added: "This coming year, I just want it to be huge for us, really. I want to keep those pacy stories, I want to keep the Bartons, Cain, Moira, the Dingles - all those characters that everybody loves - right at the forefront.
"And Home Farm, Charity, Declan - I'm loving that kind of Macbeth story where they're very dark. We'll see if they get their comeuppance soon - I'm sure they will."
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