A Massachusetts girl is recovering in the hospital after being diagnosed with a life-threatening illness linked to the flu.

Back in December, Althea’s flu symptoms worsened from a fever to dizziness and then a seizure, WHDH 7News reported. Having visited Mass General Hospital, the 4-year-old was diagnosed with Acute Necrotizing Encephalopathy, a rare condition associated with the flu that causes the brain to swell.

“It was very clear that something was not right and even though she was having a seizure, she was very sleepy from the inflammation,” Althea’s mother, Caitlin Lyons, told the outlet. “If she’d not been so sleepy, I would have even skipped the pediatrician but gone right to the emergency room.”

Althea spent time in the ICU as doctors raised concerns about whether she’d survive the illness.

“It came out of nowhere. Quite literally healthy one day and on death’s door the next. We could never have done anything to prevent (it),” Lyons told WHDH 7News.

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The flu spread quickly among kids and staff at Althea’s daycare in Framingham, with between 15 and 20 cases, director Carol Ann Ritter told CBS News

“We were sending children home with one symptom that could have been nothing but ended up being the flu,” said Ritter. “So just kind of going with the teacher’s instinct of being like, ‘OK, we’re being overly cautious and I’m so sorry, I know you need to send your child to care, but at this point, children are dying from this.’ ”

Althea remained in the hospital over Christmas, Ritter revealed on a GoFundMe set up on her family’s behalf.

“We are coming together as a school community to support one of our families during an unimaginable time,” Ritter wrote on the fundraiser. “Their 4-year-old daughter recently contracted Flu A, and in a devastating turn of events, instead of her body fighting the virus, it attacked her brain.”

She continued, “What began as the flu quickly became life-threatening. Her family spent nearly two weeks in the ICU …. not knowing what the outcome would be for their child.”

The fundraiser has raised over $12,000 towards its goal of $14,000 to support Althea’s family in paying for medical costs, specialized therapies and rehabilitation services for the 4-year-old.

Althea’s family was reportedly told by doctors that only about 10% of children survive Acute Necrotizing Encephalopathy, per WHDH 7News. Her mother, Lyons, believes that vaccination may have been what saved her life.

“It was just luck, and medical intervention, and acting quickly. It’s a miracle that she’s here with us and doing as well as she is,” said Lyons of Althea.

The mom added, “She’s not totally there yet, her fine motor skills have deteriorated and she’s got a bit of a shake right now, that is something we’ve been told should correct itself over time.”

Althea is expected to fully recover in three to six months, according to WHDH 7News.