The Jesuit online newsletter Province Express reports that Fr Brennan was taken to hospital on Wednesday and diagnosed with acute renal failure.
Fr Brennan, who is a Professor at the Australian Catholic University and the Notre Dame, fell ill after travelling to Papua New Guinea as a chaplain for students from Sydney's St Ignatius Riverview College on a trek along the Kokoda Trail, which culminated in the celebration of the Eucharist on Anzac Day morning.
According to the report, despite days of pain and acute discomfort, there are positive signs of recovery under the care of doctors in the Renal Unit at the Royal North Shore Hospital in Sydney.
At the moment, Fr Brennan is too weak to have any visitors other than family and Jesuits. He is expected to be in the hospital for the next 10 days.
The National Trust named Fr Brennan a Living National Treasure in 1998 for his involvement in Indigenous issues.
He has been recognised with numerous awards for his work, including the Humanitarian Overseas Service Medal and the Order of Australia.
Frank Brennan falls ill (Province Express, 3/5/07)
LINKS (not necessarily endorsed by Church Resources)
ACU National | Frank Brennan SJ, AO
Frank Brennan SJ Profile (Uniya)
Saint Ignatius' College, Riverview, Sydney, Australia
Frank Brennan, Building Capacity and Durability in Schools (2007 Senior Staff Conference, Westminster School Adelaide, 15/4/07)
Don't lift ban on cloning, says Brennan (CathNews, 23/6/06)
Aboriginal leader's critique of Brennan speech (CathNews 4/6/04)
4 May 2007