"Time is running out to save our daughter," Glenn O'Neill says about his daughter Eliza, who suffers from Sanfilippo syndrome

Credit: O'Neill Family

This winter, Eliza O’Neill’s elementary school had a Frozen-themed dance, but the five-year-old was nowhere in sight.

Instead, she was at home in Columbia, South Carolina, with her parents and older brother – a place that has become her safe haven for the past nine months.

Eliza suffers from a rare, ultimately fatal genetic disorder called Sanfilippo syndrome, type A.

She is slowly losing her ability to speak and by the age of six she will most likely not be able to talk at all. By ten, most children with the disease are wheelchair bound and need have around-the-clock care.

Since Eliza’s July 2013 diagnosis, her parents, Glenn and Cara, have been doing everything in their power to give their daughter a chance to survive – even if that means having to raise $2.5 million.

“We heard that there was a clinical trial that might cure Eliza of this disease,” Glenn, 42, tells PEOPLE. “So of course we knew that we had to raise every dollar that they needed for it.”

Through a GoFundMe page and traditional fundraising, they met their goal last December.

By now, Glenn and Cara thought the clinical trial would have started. But instead, there are difficulties in the drug production. They wake up every morning hoping it will be the day they get a call that it’s moving forward at a faster speed.

“This is our only chance,” Glenn says. “Not only for Eliza, but other children with Sanfilippo.”

Even when the medicine is ready, the O’Neills don’t even know if Eliza will be picked for the trial.

“We can only hope,” he says.

Nine Months Inside

Two large sheets of paper hang on the O’Neills’ kitchen wall with the number 280 written on it. Below it are two smiley faces and the phrase “stay positive.”

Every day, the number gets higher, which is just another reminder of how many days they have been living in self-imposed quarantine.

It might sound drastic, but Glenn and Cara made this tough decision because they don’t want Eliza to get sick.

“We have heard from other parents who have children with Sanfilippo that if their child gets sick at this critical age, it could accelerate their Sanfilippo symptons,” Cara, 40, tells PEOPLE.

Less time around other people means there is a smaller chance she could catch even the common cold.

They also don’t want Eliza to become immune to the AAV9 virus that she would be receiving as part of the trial.

If she and her family interact with other people, she could catch the virus, which doesn’t show any symptoms, and her body would reject the gene therapy. When it comes time for the trial, she wouldn’t be able to take part in it.

“This is a personal decision that we made,” Glenn says. “Doctors understand why we’re doing this but they didn’t tell us we had to.”

Cara had to quit her job as a pediatrician while Glenn is able to work remotely as a consultant at Symantec.

“We think about how we are keeping our daughter at home during the days which could be the best she ever has,” says Glenn. “We can’t take her to the zoo or the playground and she isn’t in school with other kids.”

Their son, Beckham, 8, also had to be taken out of school and can participate remotely. Although he misses his friends, he understands the situation they’re in.

“I don’t want her to have Sanfilippo anymore,” he tells PEOPLE. “It messes up her brain and I want her brain to be normal.”

He also enjoys the time he spends with his sister, knowing that the good times they share could be limited.

“My favorite thing to do is wrestle with her. We also like to jump on the beds,” he says. “She’s funny and likes to wear my clothes. At bedtime, she’s soft and snuggly.”

The O’Neills get their groceries delivered and on the rare occasion they do have to interact with people, they wear masks and gloves.

The family leaves their house about once a week to go to an empty beach or field, where Eliza and Beckham can run around and ride their bikes.

“That’s really the only safe place we can go,” Glenn says. But inside their home, they have gotten quite creative with how to keep busy.

For Valentine’s Day, Glenn thought about the school dance Eliza missed, so he decided to bring the dance to them.

“We got dressed up and had a dance party,” Glenn says.

They also started their own Dancing with The Stars competition where they put their iPod on shuffle and judge each other’s dancing skills.

The family plays make-believe in the backyard, lets Beckham give them haircuts and the walls of their house have become a place to create artwork.

“The walls are not off limits,” Glenn says. “Eliza draws random things and Beckham draws pictures of Chinese villages he’s learning about in his Chinese class.”

As Glenn and Cara try to keep their children busy, they can’t help but ask each other if they’re doing the right thing.

“I can’t say if looking back one day I would regret anything we have done for Eliza and Beckham,” Glenn says. “We constantly make sure we both still agree that this is the right move.”

At one point, they considered having Beckham live with his grandmother near by but decided it would be best for the family if they all stayed together.

“He said he didn’t want to leave us but he especially didn’t want to leave Eliza,” says Glenn.

The O’Neills can’t help but think about all of the things they can’t do when they see their friends posting on Facebook about living their normal lives.

With no clear sight of when the trial will begin, Glenn doesn’t know how long they will continue to live in isolation.

“If they tell us that it’s going to be another year, are we really going to continue doing this?” he says. “I have no clue.”

Eliza’s Future

Every day, Glenn and Cara look at Eliza and hope that she can still recite the alphabet and count numbers in order.

“This might not stand out to most parents,” says Cara. “But it makes me proud and gives me a hope.”

When they look at their daughter, they know that she is not where she is supposed to be at her age.

“She’s fighting to continue to know the things she knows,” Glenn says. “But most children with Sanfilippo at her age can’t even speak anymore.”

While they count their blessings, they see the disease slowly taking over.

“When I look at videos of her from a year ago, I know something is different. The quality of her speech has changed,” Cara says.

The O’Neill’s say they will never give up.

“We are racing for Eliza and other kids to get this clinical trial before they have lost their ability to function and have a good quality of life,” Glenn says. “I can only see as far as the day Eliza gets the drug, ” he says. “And I will do everything I can to make sure that happens.”