Infectious diseases specialist Dr Karina Kennedy and colleagues said they recently treated two piggery workers from the same unidentified NSW town with Streptococcus suis, a disease which affects the heart valves.

Only two cases of human infection had previously been reported in Australia one in 1993 and one last year involving a 41-year-old man who worked as a pet food processor.

The first patient, treated at Canberra Hospital two years ago, was a previously healthy 46-year-old woman whose job involved ''hands-on work'' in the piggery.

She had experienced fatigue, night sweats and had lost 20kg in the three months before she arrived at Canberra Hospital.

She was treated with antibiotics and had surgery to replace a severely damaged aortic valve.

The second patient was a man, 58, who went to Canberra Hospital early this year, suffering from similar symptoms.

''He had been unwell for about one month with fevers, sweating, fatigue and weight loss of 6kg,'' Dr Kennedy said in the latest Medical Journal of Australia, out today.