[4] Horvath practiced for 30 years at Royal Prince Alfred Hospital in Sydney, including as director of renal and transplant services between 1997 and 2003.
[5][6] He is distinguished as having been the late Kerry Packer's nephrologist and was instrumental to the Royal Prince Alfred Hospital's profile as a kidney-transplantation facility.
Horvath was also deputy chair of the World Health Organization's international cancer research institute in Lyon in France.
[5] Horvath served as the Chief Medical Officer of Australia and chaired the National Influenza Pandemic Action Committee.
In planning Australia's response to a flu pandemic, Horvath said, alluding to measures that have been used in the years since his tenure as the Chief Medical Officer, "There's lots of things we could do before border closures: alerts, screening, being aware one of our neighbouring countries has a high-level alert … then there's the no-brainers: we want to make it socially unacceptable to go to work coughing, spluttering, infecting the entire staff.