Australian and New Zealand hospitals have dramatically improved the survival chances of people admitted to intensive care units (ICUs) with severe infections, according to a 12-year study.

The improvements are so good that patients in the two countries are more likely to survive than anywhere else in the world, says study co-author Associate Professor David Pilcher, of the Australian and New Zealand Intensive Care Society.

He and colleagues from Monash University reviewed more than 100,000 patients treated in 171 ICUs from 2000 till 2012.

At the start of the study patients had a 34 per cent chance of dying. That figure was slashed to 18.4 per cent by 2012.

The number and severity of infections increased over the period of the study, says Pilcher.

‘‘We don’t know the specific reasons,’’ he says. ‘‘It could include greater recognition of infections in wards or the emergency departments.‘‘An increasing incidence of antibiotic-resistant bacteria could be a factor.’’

People with severe infections, commonly known as septicemia, are the most common emergencies treated by ICUs and make up almost 10 per cent of the 1,037,115 patients treated at the ICUs over the period.

Elderly people and those with compromised immune systems are most at risk, but patients could become severely infected after an operation or as a complication from pneumonia or another illness. There was also an overall improvement in ICU survival during the period, according to the study, which is published in the Journal of the American Medical Association.

Pilcher says there is a gap in information about what happened to ICU patients after they were discharged from hospital.

‘‘Many people go to rehabilitation centres, chronic care facilities and nursing homes. We don’t know what happens to them next.

‘‘We don’t know if they can walk and talk and feed themselves or if they are alive one year later.

‘‘This is a positive story. But if we are going to continue to improve we need to know how well these patients do when they leave. That’s our next area of focus.’’

He said there was no single reason for the improvement.

‘‘It’s not due to a magic bullet or a specific antibiotic or therapy,’’ he said. ‘‘This reflects overall good care.

‘‘It is partly due to the training of nurses and doctors, and good facilities.

‘‘It is also due to the ability to provide 24-hour one-on-one nursing for every patient.’’