A girl who inspired medical marijuana reform has died from a virus that is suspected to be related to the coronavirus.

Charlotte Figi, 13, from Colorado Springs, Colorado, died on Tuesday after previously being hospitalised for pneumonia, breathing problems, and seizures.

Her mother, Paige Figi, said on Wednesday the child was treated as a likely Covid-19 positive case even though she tested negative for the novel virus.

"It is with a heavy heart that we write to let you know that Charlotte Figi passed away yesterday," Mrs Figi wrote in a Facebook post. "Charlotte's story directly impacted thousands of families across the globe and has changed the face of cannabis in many ways."

All five members of the Figi family were sick last month from "fevers, pains, coughs" and some were "struggling to breathe", according to a Facebook post on 26 March.

While most of the family soon recovered from the virus, Charlotte did not improve.

Charlotte gained notoriety around the world after she was featured in a documentary titled Weed in 2014, and her story was narrated by CNN Medical Correspondent Dr Sanjay Gupta.

The child was diagnosed with Dravet syndrome, a rare form of epilepsy unable to be controlled with medication, after experiencing seizures starting at just three months old. Due to the syndrome, Charlotte would experience as many as 300 grand mal seizures per week, which put her in a wheelchair and caused cardiac arrests.

But her situation improved after the Stanley Brothers, medical marijuana growers in Colorado, bred a plant with low THC levels, which causes the high marijuana users experience, and high CBD levels.

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After taking the CBD oil, Charlotte saw a sharp decline in her seizures and an improved quality of life. She initially was not expected to live past the age of 8, but the child beat that estimate.

The extract the Stanley Brothers created was later called "Charlotte's Web" in honour of the child.

Charlotte's recovery inspired her family to travel around the nation to help curb the stigma surrounding medical marijuana. It also encouraged her mother to start a non-profit called Realm of Caring, which pushed for more research into the benefits of medical marijuana.

"Charlotte was ten feet tall and carried the world on her shoulders," the Stanley brothers wrote in memorial for the child.

"Inspiring is a lacking word, as are courageous and vivacious and strong and beautiful. She was divine," they added. "She grew, cultivated by a community, protected by love, demanding that the world witness her suffering so that they might find a solution. She rose every day, awakening others with her courage, and with that smile that infected your spirit at the cellular level."

CNN also memorialised Charlotte on Thursday with the help of Dr Gupta, who formed a close bond with her when filming the documentary.

He said Charlotte helped him recognise, as a medical professional, the potential benefits of medical marijuana and how it could impact patients' lives.

"Charlotte changed the world. She certainly changed my world and my mind," Dr Gupta wrote in an op-ed for CNN. "She opened my eyes to the possibility of cannabis being a legitimate medicine. She showed me that it worked to stop her crippling seizures, and that it was the only thing that worked. She was proof that withholding a medication, even one that comes in the form of a plant, would be as much a moral failing as a medical one."

Both he and CNN's Poppy Harlow got choked up on air when talking about Charlotte and the difference she made.