Ella Dawson expected to find a Netflix bill in her Brooklyn mailbox. She discovered instead a letter from Hillary Clinton. The 24-year-old blogger, who writes often about living with genital herpes, figured it was a standard campaign mailer. She once donated $50 to Clinton.

She tore open the envelope. She froze. Did the Democratic presidential candidate, one of the most famous figures on the planet, just thank her for talking about sexually transmitted infections on the Internet?

“I am so grateful to you for not only speaking out against the stigma,” Clinton wrote, “but for also taking a courageous stand against the ridiculous, but very real, barrage of hate you received online.”

Dawson shared a photo of the letter Tuesday with her 7,600 Twitter followers:

Messages poured in:

Thank you for standing up.

I'm sorry you have had to suffer harassment, Ella, but thank you for fighting.

#UglyCrying too!! There are so many of these personal stories out there!

Politics aside, Dawson hopes the high-profile recognition will help change the way people talk about herpes — a condition she says is misunderstood and common. Two out of three people under the age of 50 have Herpes Simplex Virus 1, which can cause oral and genital sores, according to a January report by the World Health Organization.

That amounts to roughly 3.7 billion people with an incurable virus. Doctors say the majority never see an outbreak.

The Centers for Disease Control, meanwhile, reports one in six Americans, ages 14 to 49, have genital herpes. Still, those who catch it often say they feel isolated. One survey respondent with an STI told researchers in a 2011 study they felt like “less of a person.”

Jenelle Davis, founder of The STD Project, blames the stigma. In popular culture, people with herpes (or other sexually transmitted infections) come off as dirty, promiscuous and irresponsible. In reality, they could be anyone who has had skin-to-skin pelvic contact with another human.

Sex education, as its commonly taught in American schools, can exacerbate the stereotype, advocates say. Students often learn STIs are consequences of actions but not what they should do if they catch one.

“We get emails from people pouring their hearts out,” said Davis, who runs a web community that debunks STI misconceptions. “They say it’s because of you that I’m starting to date again, or it’s because of you that I no longer feel like trash.”

Dawson’s diagnosis came days before she turned 21, she told The Post, and the news left her confused. She said she used condoms, but didn’t know herpes spreads through skin-to-skin contact and latex doesn’t always stop it. She feared she could never enjoy intimate relationships again.

But the fear of people judging her was actually worse — much worse — than the physical symptoms, Dawson said. She learned ways to greatly reduce risk of transmission during sex. Men and women who are not having active outbreaks, use protection and take daily antiviral therapy run a roughly 2 percent risk of passing the infection to a partner, medical research suggests.

“It’s not a conversation most people are having,” said Dawson, who works for the nonprofit Ted Talks.

She wanted to spark dialogue and grow a support network. So, she started chronicling her experience online. She wrote an essay last year for Women’s Health called “Why I love telling people I have herpes.” She said people, to her face, generally responded with curiosity and respect — "What’s it like?" — or enthusiasm: "Me too!" Online, though, she became a target for harassment.

“What a stupid feminist, wanting the social acceptance of herpes,” she wrote, summarizing the onslaught of comments. “Get a real problem, and don’t make such terrible life choices, you disgusting slut. YouTube commenters have told me to do the world a favor and kill myself.”

In May, Dawson told students at Connecticut College she wasn’t trying to glamorize herpes. She’s not proud of it — she just isn’t ashamed of it. 

“Telling someone that you have an STI should not be brave or shocking,” she said. “It should be normal and kind of boring.”

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