A human rights lawyer has accused the Federal Government of failing "in its duty of care" after a 15-month-old girl housed in a Melbourne immigration detention centre was hospitalised with the flu.

Key points: Isabella is being treated at the Northern Hospital in Epping for Influenza A

Isabella is being treated at the Northern Hospital in Epping for Influenza A The 15-month-old has been sick for weeks but was only hospitalised after her mother's lawyer phoned for an ambulance

The 15-month-old has been sick for weeks but was only hospitalised after her mother's lawyer phoned for an ambulance Her mother, Huyen Tran, gave birth to Isabella in detention after fleeing Vietnam

Vietnamese asylum seeker Huyen Tran was put in detention about 20 months ago, when she was about 5 months pregnant with her daughter Isabella.

Baby Isabella was born in detention and according to the pro-bono legal firm Human Rights for All, she has spent her entire life in detention.

Ms Tran's lawyer, Alison Battisson, told the ABC that Isabella's mother had been complaining to staff at the Melbourne Immigration Transit Accommodation (MITA) facility for several weeks that the 15-month-old had a fever, but those calls were ignored.

Ms Battisson said an ambulance was called to MITA, at Broadmeadows in Melbourne's north, on Friday evening.

"It should not take somebody's lawyer calling ambulance services for a baby's temperature to be checked. It is just insane," she said.

Isabella, who is one of five children in detention at MITA, has been diagnosed with Influenza A.

"The flu in a child can be quite serious," Ms Battisson said.

A lawyer acting for Isabella's mother called the ambulance. ( Supplied: Human Rights For All )

The Australian Border Force (ABF) would not comment on the case, but said healthcare services for detainees and their relatives "are comparable to those available to the Australian community under the Australian public health system".

Northern Health has confirmed it is caring for Isabella.

"The child is currently being treated for a medical condition as an inpatient at Northern Hospital Epping," the health service said in a statement.

Huyen Tran fled Vietnam over fears of persecution due to her Catholic faith.

Ms Tran is also sick and receiving hospital treatment.

Ms Battisson said the centre was not the place for children.

"Places of detention are just inherently unsafe for children, you cannot make them safe," she said.

"The mothers cannot provide a safe space for them in terms of hygiene and sanitation."

Isabella's transfer to hospital follows the death of a 23-year-old Afghan man, who died at MITA on Friday night.

His death is not being treated as suspicious and a report is being prepared for the coroner.

"This is the type of environment they are exposed to," Ms Battisson said.

"Yes, they might be held in different living areas, but the communal areas, the visiting areas are all the same."

In a statement, ABF said healthcare was provided at its facilities "through on-site primary and mental health clinics with referral to allied and specialist health providers, as required".

"The Department does not comment on individual cases."