Protesters have blasted the federal government after a 15-month-old girl who has spent her whole life in immigration detention in Australia was rushed to hospital with the flu.

Baby Isabella Lee Pin Loong is the daughter of Vietnamese woman Huyen Thu Thi Tran, an asylum seeker detained at Melbourne Immigration Transit Accommodation (MITA) since she was about five months pregnant.

Isabella was rushed from the government-run facility to Northern Hospital with Influenza A on Friday, where she remains with her mother.

A group of protesters gathered at the hospital on Wednesday morning and demanded the the pair not be returned to MITA.

“It breaks my heart,” Amelia Christo of the advocacy group Mums4Refugees told SBS News.

“[Isabella] has a whole heap of anxiety issues, having been in detention since she was born and with a mother who’s very distressed. It’s nowhere for a child to be brought up,” Ms Christo said.

“My son had Influenza A this year … My heart goes out to this mother with a very sick child.”

Fellow protester Huong Truong said Isabella “fell sick a couple of weeks ago and it wasn’t until a lawyer rang that she was properly seen to and an ambulance came”.

“She is not being looked after like any other Australian kid.”

A spokesperson for Northern Health confirmed Isabella is being treated at Northern Hospital but could not provide further details.

In a statement, Australian Border Force denied Isabella was being detained.

“Her mother is detained and her father lives in the community. The infant has been living with her mother at her request, but may come and go from the facility and stay in the community with her family,” the statement read.

It also said the infant received proper medical care at the facility.

“A range of care, welfare and support arrangements are in place to provide for the needs of children and young people in detention,” it said.

However, advocates have challenged the idea that Isabella can freely “come and go”, due to the circumstances of her mother.

The UN Working Group on Arbitrary Detention has looked into the matter and challenged the notion that Ms Tran is opting to let Isabella stay with her under “guest” status.

In a report last month, it said “the requirement for Ms Tran to sign the request to allow her child to remain with her as a ‘guest’ in the detention facility is nothing more than an attempt on behalf of the authorities to circumvent the prohibition of detention of children in the context of migration”.

The UN group called for Australia to release them immediately “and accord them an enforceable right to compensation and other reparations”.

Ms Tran, a Catholic, says she fled religious persecution from rural Vietnam and landed on Christmas Island by boat in 2011. On arrival, she was put in detention where she stayed for more than a year.

In 2012, Ms Tran then lived in Australia under a community detention arrangement, which she says she violated to avoid deportation.

Before authorities relocated her in 2017, she married and got pregnant. She was at that point taken to MITA. Isabella was born a few months later and remains stateless.

It is the latest incident to occur at MITA, coming only days after one man died at the government facility and another was taken to hospital after trying to set himself on fire.