Alyssia Brown knew how to make people feel special.
"She was the person that literally anybody could call for anything and she would drop what she was doing and be there in a heartbeat," her sister, Amity Brown, tells PEOPLE. "It didn't matter if she was five miles away from where you're at or 5,000 miles away. She would figure out a way to get there and be there for you."
Amity, 30, lived three hours away from her older sister in Tennessee. She was wrapping up nursing school in Knoxville while Alyssia, 39, drove for different delivery services around Nashville.
"We talked a lot on the phone," Amity says. The sisters "talked about nothing and everything," with Alyssia often mentioning the multiple construction sites she would see on her drives.
"She mentioned it a lot to me in passing like, 'I wonder what they're building,' " Amity says.
She was living in the June Lake area, a Spring Hill development where "they were doing a lot of excavating" -- and Alyssia suggested there might be a new house that her sister could move into, so they would be closer together.
But toward the end of October 2025, Alyssia began to feel unwell. She had previously been diagnosed with sarcoidosis -- inflamed bumps in the lungs called granulomas -- which can cause shortness of breath and chest pain. For Alyssia, it meant she struggled longer with bronchitis and respiratory infections. So at first, Amity says her sister dismissed her symptoms as her usual experience with granulomas.
By Nov. 2, when Alyssia came to Amity's 30th birthday party, her voice was hoarse. Still, she thought it was just an upper respiratory infection.
On Dec. 8, Alyssia called her sister, saying, "I woke up and all my joints hurt.' And that's the part that that worried me immediately," says Amity, who encouraged her sister to go to the emergency room.
None of the tests showed anything -- because no one tested for histoplasmosis.
The fungal infection is caused by inhaling spores commonly found in bat or bird feces, according to The Mayo Clinic. Although most people won't show symptoms if they're exposed, those that do -- mostly infants or those with compromised immune systems -- usually see flu-like symptoms between 3 to 17 days after exposure. These include fever, chills, headaches, dry cough and chest pain.
The spores, when present in soil, can be disseminated into the air if the ground is disturbed, Mayo Clinic explains. It's endemic to Tennessee, according to the Tennessee Department of Health.
Because of her history, Alyssia was sent home with an inhaler and steroids, "basically telling her she had bronchitis," Amity tells PEOPLE. But Alyssia’s condition continued to deteriorate. She had chest pains. A nosebleed. She felt fatigued.
Then on Dec. 12, an article on histoplasmosis crossed their mother Gwendolyn’s Facebook feed. She sent it to her daughters, and Amity told her sister to go to the emergency room and get tested immediately.
On Dec. 13, Alyssia returned to the emergency room with her roommate, where she was told, “You don’t look like people who have histoplasmosis look. They look a lot sicker than you look.’ ”
Amity shares that “They were begging, like, ‘Please just test her for this ... we just want to make sure she’s okay because she’s been sick since October.’ ” Finally, Alyssia’s urine was tested and she was told to wait for her results.
“I talked to her on the night of the 14th and she said that ‘I still don’t feel great,’ but shared they prescribed her an antibiotic. Alyssia was feeling hopeful that ‘finally I’m gonna have some answers and finally I’m gonna feel better,’ ” Amity says.
“That was the last conversation I had with her,” she tells PEOPLE. The next day, Dec. 15, her roommate found Alyssia dead on the floor of her bedroom. Three days later, the hospital called, saying that her test for the histoplasmosis came back with a “critical high level in her urine, and she needed to come in immediately for treatment.”
Alyssia died nearly two weeks after the Tennessee Department of Health first confirmed a histoplasmosis outbreak on Dec. 3, after 18 people were confirmed to be sick with the illness. In a statement, the department said there was "an increase in acute and severe histoplasmosis cases occurring in residents of Spring Hill and Thompson's Station, starting in September 2025."
Spring Hill, of course, was where Alyssia lived.
"A clear source of exposure has not been identified, which is not uncommon related to histoplasmosis," the Department of Health told PEOPLE in January. "Histoplasmosis is commonly found throughout the soil in Tennessee, so it can be challenging to completely prevent exposure. Those who have weakened immune systems or are exposed to a large amount of histoplasmosis spores face a higher risk of severe infection."
Construction was questioned as the source of the outbreak, ABC affiliate WKRN reported. The latest data says 35 people in total have been sickened, with one fatality.
That one fatal case -- Alyssia -- was "full of life," her sister says. "Now she can't continue to go on. All of the things that she wanted to do with her life, she can't do any of those things because somebody let that slip through the cracks because they didn't test her for it," Amity tells PEOPLE.
"I lost my big sister and my mom lost her daughter and her friends lost their best friend and everybody lost a confidant," Amity tells PEOPLE.
Although Amity admits "talking about my sister's legacy is really hard for me," she says Alyssia "loved people. She loved to make a difference in somebody's life."
That's why Amity is sharing her sister's story and raising awareness of the endemic nature of histoplasmosis, which is treatable if diagnosed. As the U.S. Centers for Disease Control points out, histoplasmosis can be treated with antifungal medications.
"I think that, in her death, if it meant that the next person got to live, that would make her happy," Amity says. "She would truly be like, my life meant something because I saved that next person from not having to go experience what she had to experience."
Never miss a story -- sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from celebrity news to compelling human interest stories.
"If sharing her story sheds light on things that are maybe broken in the system when it comes to histoplasmosis or sheds light on testing for histoplasmosis -- or just how to treat your patients -- my biggest hope is that their takeaway is that,'I need to do better and we need to do better,'" she says.
"It's not a hard test. It shouldn't be something that you have to beg for. You should be able just to get tested for it," Amity says. "It doesn't matter if it feels silly. It matters that that person gets to be alive and spend time with their family."