A rare immune disease has left a 4-month-old girl from Uitenhage fighting for her life. Little Leah de Jager is being treated in the intensive care unit of the Dora Nginza Hospital in Port Elizabeth after being diagnosed with severe combined immunodeficiency (SCID). The rare, life-threatening illness occurs in one in 40 000 to 100 000 births and has a severe effect on children's immune systems.Read more about SCID here: Severe combined immunodeficiencyAccording to Leah's father, Gerrit de Jager, 32, a radio DJ and entertainer, she became increasingly quiet when she was around three months old. "My wife Lezaan and I googled her symptoms and found that many babies react the same way during growth spurts. We weren't really that concerned. "But on October 6 she got a fever which didn't go away with treatment. We got her to a paediatrician who gave her one look and admitted her to hospital."De Jager told News24 on Wednesday that, at this point, Leah was struggling to breathe and her oxygen levels were low.'Bills were piling up'Leah was admitted to the Netcare Cuyler Hospital in Uitenhage 15 days ago where she was initially treated for pneumonia. "When she didn't respond to treatment, the doctor realised something was wrong."After running blood tests, Leah was diagnosed with SCID and moved to intensive care. "At this point my medical bills had piled up to about R200 000," De Jager said.Leah de Jager with her mum, Lezaan (Facebook) "So I told the doctor I was going to take out a second mortgage to help keep her in hospital. He then pulled me aside and said I was going to ruin myself financially."Leah was then moved to the provincial government Dora Nginza Hospital, where, initially, her condition worsened considerably. According to De Jager, this was owing to Leah initially having been treated for the wrong illness and in the wrong conditions, prior to being transferred. She remains under sedation at Dora Nginza Hospital, which De Jager says has "a phenomenal intensive care unit".'It's a Catch-22 situation'De Jager says Leah is fighting off a viral infection. "It's a Catch-22 situation, because she doesn’t have the immune system to fight it and antibiotics won’t help either."WATCH: The story of Ayaan Ahmed, Cape Town's very own 'Bubble Boy'De Jager says a well-doer offered to have a specialist flown in and to pay for medication from overseas, but her doctor said there was nothing that could be done except to wait for Leah to get better and to pray."Obviously, that’s not the kind of thing you want to hear from a specialist."De Jager says he believes that prayer and faith have had a positive effect on Leah and that her condition was improving. She is not out of danger by a long shot, though. De Jager says an MRI revealed that Leah had suffered damage to parts of her brain comparable to having a stroke, but that she was now recovering. "They are starting to bring her out of sedation little by little. Now we play the waiting game. The next 36 hours will be critical.'God will heal her'"I don't care what anyone else believes – I believe that God will heal her 100%."I told the doctor, she will get out of here – no matter what happens."Once Leah recovers, she would be treated with immune boosters every seven days and sent home. "But ultimately she would have to receive a bone marrow transplant."De Jager says because the disease is genetic, Leah's family could not be considered as donors. "We have a number of months lying ahead of us. "For now, I want to create as much awareness around SCID as I can. Many children seemingly die of pneumonia, but the real cause is SCID. Babies need to be tested at birth to ensure their immune systems are normal so that more lives can be saved," said De Jager.Last month, Parent24 reported on the progress of Cape Town's "bubble boy", Ayaan Ahmed, who was diagnosed with SCID at eight weeks old in 2016.Ayaan's condition improved considerably after taking part in a trial by St. Jude Children's Research Hospital in Memphis in the US in 2017.